A seller hands you a pro forma showing a 12% cash-on-cash return on a 20-unit apartment in Southeast Houston. The numbers look great. Too great. You dig in, re-run the math with real expenses, and that 12% turns into 4%. Maybe less.
This is why underwriting matters. Not the seller's version. Yours.
If you're buying multifamily in Houston, the single most important skill you can develop is the ability to underwrite a deal from scratch. Not relying on a broker's pro forma. Not trusting the trailing 12 months at face value. Building your own model with real Houston numbers, real tax rates, and real vacancy assumptions.
This guide walks you through the entire process. Every line item. Every formula. With a full example deal so you can see how it all connects.
What Underwriting Actually Means
Underwriting a multifamily deal means building a financial model that answers one question: does this property make money after all expenses and debt service?
That sounds simple. It's not. Because every line in your model is a judgment call. What vacancy rate do you assume? Are the seller's reported expenses accurate? Is the rent roll inflated with concessions that expire next month?
Your job as the buyer is to stress test every assumption. Lenders will do their own underwriting, but yours needs to be tighter. Because the lender's downside is a foreclosure. Your downside is your entire investment.
Step 1: Gross Potential Rent (GPR)
Start at the top. Gross Potential Rent is the total income the property would generate if every unit were occupied at market rent with zero concessions.
For a Houston multifamily property, you need to verify two things:
- Current rent roll accuracy. Get the actual signed leases. Compare them to what the seller claims. Look for month-to-month tenants (higher turnover risk), below-market units (upside potential), and above-market units (retention risk).
- Market rent comps. Pull comps from CoStar, Apartments.com, or local property managers. Houston rents vary wildly by submarket. A 2BR in Montrose commands $1,500+. That same unit in Greenspoint might get $850.
For our example deal, let's use a real scenario. A 16-unit property in the Spring Branch area. Mix of 1BR and 2BR units.
| Unit Type | Count | Monthly Rent | Annual Rent |
|---|---|---|---|
| 1BR / 1BA | 8 | $1,050 | $100,800 |
| 2BR / 1BA | 8 | $1,300 | $124,800 |
| Gross Potential Rent | $225,600 | ||
Other income matters too. Laundry, parking, pet fees, late fees, application fees. For Houston multifamily, other income typically runs 3% to 5% of GPR. We'll use $8,400/year ($525/month), which puts our Gross Potential Income at $234,000.
Step 2: Vacancy and Credit Loss
No property stays 100% occupied. You need a vacancy factor that reflects reality, not optimism.
Houston's overall apartment vacancy rate hovers around 8% to 10% depending on the submarket and property class. Class A properties in the Energy Corridor or Katy might run 6% to 7%. Class C properties in Northeast Houston or Greenspoint can hit 12% to 15%.
For our Spring Branch 16-unit (Class B), we'll use 8% vacancy and credit loss. That's conservative but realistic for that submarket.
$234,000 x 8% = $18,720 in vacancy loss
Effective Gross Income (EGI): $215,280
Red flag in seller pro formas: Watch for vacancy assumptions below 5%. Some sellers will show 3% vacancy on a Class C property. That's fiction. Always use your own vacancy number based on the submarket and property class. Check our Houston rental property analysis guide for current vacancy data by area.
Step 3: Operating Expenses (Where Deals Die)
This is where most new investors get burned. Operating expenses in Houston are higher than many markets, and the biggest reason is property tax.
Property Taxes
Texas has no state income tax. The tradeoff is aggressive property taxes. Harris County's effective tax rate runs about 2.0% to 2.3% of assessed value. For investment properties, especially after a sale, expect the appraisal district to reassess close to your purchase price.
If you're buying our example property for $2,100,000, budget property taxes at roughly 2.1% of that number: $44,100/year. That's the single largest operating expense. For more detail on how this works, read our Houston property tax guide.
Insurance
Texas insurance costs have climbed significantly since 2023. For a 16-unit multifamily in Houston, expect to pay $800 to $1,200 per unit per year depending on age, construction type, flood zone status, and claims history. We'll use $950/unit: $15,200/year.
If the property sits in a FEMA flood zone, add another $200 to $500 per unit for flood insurance. Check our Houston flood zone guide before making assumptions here.
Full Operating Expense Breakdown
| Expense Category | Annual Cost | Per Unit | % of EGI |
|---|---|---|---|
| Property Taxes | $44,100 | $2,756 | 20.5% |
| Insurance | $15,200 | $950 | 7.1% |
| Repairs & Maintenance | $14,400 | $900 | 6.7% |
| Property Management (8%) | $17,222 | $1,076 | 8.0% |
| Utilities (Owner-Paid) | $9,600 | $600 | 4.5% |
| Landscaping & Pest Control | $4,800 | $300 | 2.2% |
| Administrative & Legal | $2,400 | $150 | 1.1% |
| Capital Reserves | $4,800 | $300 | 2.2% |
| Total Operating Expenses | $112,522 | $7,033 | 52.3% |
That 52.3% expense ratio is typical for Houston multifamily. Nationally, the rule of thumb is 45% to 55%. But Texas pushes higher because of property taxes. If a seller shows you an expense ratio below 40%, they're probably hiding something or self-managing with deferred maintenance.
Houston-specific note on property management: Professional management typically runs 7% to 10% of collected rent for properties under 50 units. Even if you plan to self-manage, underwrite with a management fee. Your time has value. And if you ever want to sell, a buyer underwriting your deal will include it regardless.
Step 4: Net Operating Income (NOI)
Here's the number that matters most. NOI is your Effective Gross Income minus Total Operating Expenses. It tells you what the property earns before debt service.
NOI = $215,280 (EGI) minus $112,522 (Expenses) = $102,758
This is the foundation for everything else. Cap rate. Valuation. Debt service coverage. Cash-on-cash return. If your NOI is wrong, every other number falls apart.
Compare your NOI to the seller's. If their NOI is 30% higher than yours, the gap is usually in expenses they're not reporting or vacancy they're understating. Ask them to explain every discrepancy.
Step 5: Cap Rate and Valuation
The capitalization rate (cap rate) is the ratio of NOI to property value. It's how the market prices income-producing real estate.
Cap Rate = NOI / Purchase Price
For our deal: $102,758 / $2,100,000 = 4.89% cap rate
Is that good? It depends on the submarket. Here's what cap rates look like across Houston in early 2026:
| Houston Submarket | Class A | Class B | Class C |
|---|---|---|---|
| Inner Loop (Montrose, Heights, Midtown) | 4.0% - 4.5% | 4.5% - 5.2% | 5.5% - 6.5% |
| Galleria / Uptown / River Oaks | 4.2% - 4.8% | 4.8% - 5.5% | 5.8% - 6.8% |
| Spring Branch / Memorial | 4.5% - 5.0% | 5.0% - 5.8% | 6.0% - 7.0% |
| Katy / Energy Corridor | 4.8% - 5.3% | 5.3% - 6.0% | 6.2% - 7.2% |
| Sugar Land / Missouri City | 4.8% - 5.5% | 5.5% - 6.2% | 6.5% - 7.5% |
| Spring / The Woodlands | 4.5% - 5.0% | 5.0% - 5.8% | 6.0% - 7.0% |
| Pasadena / Southeast | 5.5% - 6.2% | 6.2% - 7.0% | 7.0% - 8.5% |
| Greenspoint / North Houston | 6.0% - 6.8% | 6.8% - 7.8% | 7.5% - 9.0% |
Our Spring Branch Class B deal at a 4.89% cap rate is on the lower end of the range for that submarket. That could mean the seller is pricing aggressively, or the rents have room to grow. Either way, it tells you where you stand relative to the market.
You can also use cap rates to back into valuation. If you believe the market cap rate for this type of property is 5.5%, then the value based on your NOI would be: $102,758 / 0.055 = $1,868,327. That's a meaningful gap from the $2.1M asking price.
Step 6: Debt Service Coverage Ratio (DSCR)
DSCR tells lenders whether the property generates enough income to cover its mortgage payments. It's the most important metric in multifamily lending.
DSCR = NOI / Annual Debt Service
Most DSCR lenders want a minimum of 1.20x to 1.25x. Some agency lenders (Fannie Mae, Freddie Mac) require 1.25x. That means for every dollar of mortgage payment, the property needs to generate $1.25 in NOI.
Let's run the numbers on our deal. Assuming a multifamily loan at 6.75% interest, 30-year amortization, 75% LTV:
- Purchase Price: $2,100,000
- Loan Amount (75% LTV): $1,575,000
- Down Payment: $525,000
- Monthly Payment (P&I): $10,215
- Annual Debt Service: $122,580
DSCR = $102,758 / $122,580 = 0.84x
That's a problem. A DSCR below 1.0x means the property doesn't generate enough income to cover its mortgage. No lender will touch this deal at these terms. You'd need to either negotiate a lower price, put more money down, or find a lower interest rate.
If you negotiated the price down to $1,800,000 with the same terms:
- Loan Amount (75% LTV): $1,350,000
- Monthly Payment: $8,757
- Annual Debt Service: $105,084
- DSCR: $102,758 / $105,084 = 0.98x
Still under 1.0x. This is telling you something important about the market right now. At current interest rates, many Houston multifamily deals don't pencil at the prices sellers are asking. Learn more about how DSCR lending works in our DSCR loan guide for Houston investors.
Step 7: Cash-on-Cash Return
Cash-on-cash return measures what you actually earn on the cash you invest. It's the metric that matters most to equity investors.
Cash-on-Cash Return = Annual Pre-Tax Cash Flow / Total Cash Invested
Using our original $2.1M scenario:
- NOI: $102,758
- Annual Debt Service: $122,580
- Annual Cash Flow: -$19,822 (negative)
- Total Cash Invested: $525,000 (down payment) + $35,000 (closing costs) = $560,000
- Cash-on-Cash Return: -3.5%
Negative cash flow on a stabilized property is a clear pass. Unless you have a specific value-add plan (rent increases, expense reduction, unit renovations) that changes the NOI within 12 to 18 months, this deal doesn't work at this price.
Red Flags in Seller Pro Formas
After underwriting hundreds of deals, these are the most common tricks and oversights I see in Houston seller pro formas:
- Understated property taxes. The seller might show their current tax bill, which is based on an older, lower assessed value. After you buy at $2.1M, Harris County will reassess. Always underwrite taxes at 2.0% to 2.3% of your purchase price.
- Missing or low insurance. Some sellers show $400/unit for insurance. That might have been accurate in 2020. Not anymore. Get actual quotes before closing.
- No management fee. Owner-operators love to exclude this. Even if you self-manage, include 8% in your underwriting.
- Inflated other income. Watch for "projected" laundry income or parking revenue that doesn't match bank statements.
- 3% vacancy on a 15% vacancy property. Always verify vacancy against the actual rent roll and bank deposits.
- Deferred maintenance hidden as "capital improvements." A new roof isn't a capital improvement if the old one is leaking. That's deferred maintenance that should be reflected in your purchase price or repair credits.
- Trailing 3 months instead of trailing 12. Sellers sometimes cherry-pick their best quarter. Demand at least 12 months of financials, ideally 24.
How Lenders Evaluate Multifamily Deals
When you apply for a multifamily loan in Houston, here's what the lender's underwriter is looking at:
- DSCR. Minimum 1.20x to 1.25x for most programs. Agency loans (Fannie/Freddie) are stricter.
- LTV. Most lenders cap at 75% to 80% for multifamily. Some bridge lenders go to 80% but at higher rates.
- Debt Yield. NOI divided by loan amount. Lenders want 8% to 10% minimum. For our deal: $102,758 / $1,575,000 = 6.5%. That's too low.
- Borrower experience. First-time multifamily buyers may face higher down payment requirements or need a qualified co-signer.
- Property condition. Deferred maintenance can kill a deal. Lenders will order their own property inspection and may require escrow reserves for repairs.
- Market fundamentals. Houston's population growth, job market, and rent trends all factor in. This is one area where Houston shines for lenders.
For a broader look at investment property financing options, see our Houston investment property guide.
How to Stress Test a Deal
Good underwriting isn't about finding one set of numbers that works. It's about testing what happens when things go wrong.
Vacancy Stress Test
What happens if vacancy hits 12% instead of 8%? Your EGI drops to $205,920. Your NOI drops to $93,398. Your DSCR drops to 0.76x. If a 4-point vacancy swing breaks your deal, you don't have enough margin.
Interest Rate Stress Test
If you're getting a variable rate or a 5-year fixed with a reset, model what happens when rates increase 1% to 2%. A jump from 6.75% to 8.75% on a $1,575,000 loan increases your annual debt service from $122,580 to roughly $148,000. That turns a tight deal into an impossible one.
Expense Stress Test
Property taxes in Harris County can jump 10% to 15% in a single year after a reassessment. Insurance premiums have been climbing 8% to 12% annually in Texas. Model a scenario where total expenses increase 10%. If your deal can survive a bad year, it's a real deal. If it can't, you're betting on everything going right. That's not investing. That's gambling.
Rent Decline Stress Test
Houston's rental market is cyclical. During the 2015-2016 energy downturn, rents in some submarkets dropped 5% to 10%. If rents decline 5% and vacancy increases 2% simultaneously, does your deal still cash flow? If not, you need a bigger margin of safety or a lower purchase price.
What Makes Houston Different for Multifamily
Houston has a few unique factors that affect underwriting:
- No zoning. Houston is the largest U.S. city without traditional zoning. New supply can come online faster than in regulated markets. That puts a ceiling on rent growth in some areas.
- Property tax burden. At 2.0% to 2.3% effective rates, Texas property taxes eat a huge chunk of your NOI. In states like Florida (0.9%) or Arizona (0.6%), the same gross income produces significantly higher NOI.
- Insurance costs. Hurricane exposure, hail, and flooding make Texas one of the most expensive states for property insurance. Budget accordingly.
- Population growth. Houston adds roughly 100,000+ people per year. That's strong demand for housing at every level. For investors, this is the tailwind that keeps Houston attractive despite high operating costs.
- No state income tax. Your net returns stay higher because Texas doesn't take a cut of your rental income at the state level.
Putting It All Together
Let's revisit our 16-unit Spring Branch deal and figure out what price actually makes this work.
Working backwards from a target 1.25x DSCR and 8% cash-on-cash return:
- Required NOI for 1.25x DSCR at 75% LTV and 6.75% rate: we need annual debt service to be no more than $82,206 (NOI $102,758 / 1.25)
- Monthly P&I of $6,851 at 6.75% over 30 years supports a loan of roughly $1,057,000
- At 75% LTV, that implies a purchase price of $1,409,000
- Down payment: $352,000 + $25,000 closing costs = $377,000 total cash
- Annual cash flow: $102,758 minus $82,206 = $20,552
- Cash-on-cash return: $20,552 / $377,000 = 5.5%
To hit 8% cash-on-cash, you'd need even lower pricing or higher rents. This is the reality of multifamily investing in a higher interest rate environment. Deals that worked at 4% rates need 20% to 30% price corrections to work at 7% rates. The math is unforgiving.
That doesn't mean opportunities don't exist. It means you have to be disciplined. Underwrite conservatively. Know your walk-away number. And be prepared to make 20 offers before one sticks.
Your Underwriting Checklist
Before you submit an offer on any Houston multifamily property, make sure you've completed each of these steps:
- Verified the rent roll against signed leases and bank deposits
- Pulled market rent comps for the specific submarket
- Applied a realistic vacancy rate (8% to 10% for Class B, higher for Class C)
- Calculated property taxes at 2.0% to 2.3% of your purchase price
- Gotten actual insurance quotes (not the seller's old policy)
- Included 8% property management even if you plan to self-manage
- Budgeted $300/unit/year minimum for capital reserves
- Calculated NOI, DSCR, debt yield, and cash-on-cash return
- Stress tested vacancy, rates, expenses, and rent decline scenarios
- Compared your NOI to the seller's and identified every discrepancy
If the numbers work after all of that, you might have a deal. If they don't, move on. There will always be another property. There won't always be another $500,000 in your bank account.
Need Help Running the Numbers?
Underwriting is where good deals get made and bad deals get avoided. If you're evaluating a multifamily property in Houston and want a second set of eyes on the numbers, let's talk. I work with investors at every level, from first-time fourplex buyers to experienced operators scaling their portfolios.
I'll help you build a realistic underwriting model, connect you with the right multifamily lending programs, and make sure you're not overpaying based on inflated pro formas.
Let's look at your numbers. Schedule a free consultation or call (713) 548-7350. No pressure, no sales pitch. Just honest analysis of whether the deal works.