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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.
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.
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:
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.
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.
This is where most new investors get burned. Operating expenses in Houston are higher than many markets, and the biggest reason is property tax.
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.
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.
| 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.
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.
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.
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:
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:
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.
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:
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.
After underwriting hundreds of deals, these are the most common tricks and oversights I see in Houston seller pro formas:
When you apply for a multifamily loan in Houston, here's what the lender's underwriter is looking at:
For a broader look at investment property financing options, see our Houston investment property guide.
Good underwriting isn't about finding one set of numbers that works. It's about testing what happens when things go wrong.
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.
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.
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.
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.
Houston has a few unique factors that affect underwriting:
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:
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.
Before you submit an offer on any Houston multifamily property, make sure you've completed each of these steps:
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.
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.
About the Author: Ben Helstein is a dual licensed real estate broker and mortgage loan originator at InSync Homes & Loans in Houston, TX (NMLS #1577314, Company NMLS #1829321). He helps Houston buyers, sellers, and investors navigate real estate and financing under one roof. Learn more at https://insync.homes.
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