How to Underwrite a Multifamily Deal: Step-by-Step Guide

Multifamily underwriting is the process of analyzing a rental property's income, expenses, debt, cash flow, and returns to decide whether the deal is worth pursuing. A good underwriting process helps investors avoid overpaying, spot hidden risks, and compare multiple investment scenarios before making an offer.

In this guide, we'll walk through every step of underwriting a multifamily deal — from the documents you need, to calculating NOI, DSCR, cash flow, and investor returns, to the most common mistakes that sink deals after closing.

Watch: Multifamily Underwriting in DealWorthIt

In this walkthrough, you'll see how DealWorthIt helps investors analyze a multifamily property, review income and expenses, calculate returns, compare assumptions, and decide whether the deal is worth pursuing.

What Is Multifamily Underwriting?

Multifamily underwriting evaluates whether an apartment building or multi-unit rental property makes financial sense at a given price. It answers a simple question with a lot of math behind it: if you buy this property, what will you actually earn, and what could go wrong?

A complete underwriting covers:

• Income — current rents, market rents, and other revenue the property generates
• Vacancy — how much income you lose to empty units and turnover
• Operating expenses — everything it costs to run the property each year
• Net operating income (NOI) — income left after operating expenses
• Debt — loan terms, debt service, and how much cushion the property has to cover it
• Cash flow — what's left for investors after the mortgage is paid
• Investor returns — cash-on-cash return, IRR, equity multiple, and ROI
• Exit assumptions — what the property could sell for at the end of the hold
• Risk scenarios — what happens if rents, expenses, or rates move against you

Get the underwriting right and you buy with confidence. Get it wrong and you inherit someone else's optimistic spreadsheet.

Documents You Need Before Underwriting a Multifamily Deal

Before you build a single projection, collect the source documents. Each one verifies a different part of the deal:

Do not underwrite only from the offering memorandum. The OM is a sales document. The T12 and rent roll are closer to reality.

If you're working with T12s and rent rolls regularly, DealWorthIt can import your financial documents and parse them automatically instead of retyping them into a spreadsheet.

Step 1: Review the Rent Roll

The rent roll is the property's income engine, unit by unit. As you review it, check:

• Occupancy — how many units are actually occupied and paying
• Vacant units — how long they've been vacant and why
• Current rent — what each unit actually pays today, not the asking rent
• Lease dates — when leases expire and how much rollover risk you're taking on
• Unit types — the mix of studios, one-beds, two-beds, and their rent levels
• Delinquency — tenants who are behind on rent (occupied ≠ paying)
• Concessions — free months or discounts that inflate the sticker rent
• Loss-to-lease — the gap between in-place rents and market rents

Loss-to-lease is where the value-add story lives — and where brokers tend to be most optimistic. Compare in-place rents against verified market comps:

A real gap is upside. An imagined gap is how deals get overpaid for.

Step 2: Analyze Property Income

Start with gross scheduled rent — what the property would collect if every unit were occupied at its scheduled rent:

100 units × $1,500 average monthly rent = $150,000 monthly rent. $150,000 × 12 = $1,800,000 gross scheduled rent.

Then add other income, which can be meaningful on larger properties:

• Laundry
• Parking
• Pet fees
• Utility reimbursements (RUBS)
• Application fees
• Late fees
• Storage
• Internet and cable

Verify other income against the T12 — one-time or non-recurring items shouldn't be projected forward as if they repeat every year.

Step 3: Account for Vacancy and Credit Loss

No property collects 100% of its scheduled rent. Vacancy loss covers empty units; credit loss covers tenants who occupy a unit but don't pay. Together they turn gross scheduled income into effective gross income:

Effective Gross Income = Gross Scheduled Income − Vacancy Loss − Credit Loss + Other Income

Use a vacancy assumption grounded in the submarket and the property's actual history — not the 3% a pro forma hopes for.

Step 4: Review Operating Expenses

Operating expenses are where underwriting gets won or lost. A complete expense budget includes:

• Property taxes
• Insurance
• Repairs and maintenance
• Payroll
• Property management
• Utilities
• Landscaping
• Contract services
• Marketing
• Legal and professional fees
• Administrative costs
• Replacement reserves

Be careful with seller-reported expenses. Sellers may:

• Self-manage and report no management fee
• Defer repairs to make maintenance look cheap
• Underinsure the property
• Pay lower taxes that will jump after the sale triggers reassessment
• Use below-market payroll
• Exclude recurring costs from the statements
• Present overly optimistic "normalized" expenses

Underwrite the expenses you will actually pay — your management fee, your insurance quote, your post-sale tax bill — not the seller's history.

Step 5: Calculate Net Operating Income (NOI)

Net operating income is the single most-watched number in the deal — it drives both value and loan sizing:

NOI = Effective Gross Income − Operating Expenses

Note that NOI does not include mortgage payments, capital expenditures, depreciation, or income taxes. It measures the property's operating performance before financing and tax decisions.

Step 6: Estimate Property Value Using Cap Rate

The cap rate relates NOI to price, letting you compare deals and sanity-check the asking price:

Cap Rate = NOI ÷ Purchase Price

Value = NOI ÷ Market Cap Rate

Example: with an NOI of $892,000 and a market cap rate of 6.25%, the estimated value is $892,000 ÷ 0.0625 = $14,272,000. If the asking price is meaningfully above that, the seller is pricing in upside you haven't verified yet.

Step 7: Add Loan Assumptions

Debt shapes the whole return profile. Get a real loan quote or term sheet and model:

• Loan amount
• Interest rate
• Amortization period
• Loan term
• Interest-only period (if any)
• Loan-to-value (LTV)
• Annual debt service
• DSCR requirements
• Closing costs and financing fees

Step 8: Calculate DSCR

The debt service coverage ratio (DSCR) measures how comfortably the property's NOI covers its loan payments:

DSCR = NOI ÷ Annual Debt Service

Example: $892,000 NOI ÷ $796,384 annual debt service = 1.12 DSCR.

Many lenders want to see 1.20 to 1.30 or higher depending on the deal. A DSCR of 1.12 means a small dip in income — a few extra vacancies, a tax reassessment — could leave the property struggling to cover its mortgage.

Step 9: Estimate Cash Flow

Cash flow is what's actually left for investors after the lender is paid:

Cash Flow Before Taxes = NOI − Annual Debt Service

Then relate that cash flow to the equity you invested:

Cash-on-Cash Return = Annual Cash Flow ÷ Total Cash Invested

Example: $95,616 ÷ $4,500,000 = 2.12% cash-on-cash return. That's thin — which is exactly the kind of thing underwriting is supposed to surface before you make an offer, not after.

Step 10: Calculate Investor Returns

No single metric tells the whole story. Look at the full return picture:

A deal with a great IRR but a weak DSCR and high break-even occupancy is a deal that only works if nothing goes wrong.

Step 11: Build Multiple Scenarios

One projection is a guess. Multiple scenarios are a decision framework:

• Base case — realistic rents, vacancy, expense growth, and exit cap rate
• Downside case — higher vacancy, slower rent growth, rising expenses, and a wider exit cap rate
• Upside case — the value-add plan executes on schedule and rents hit market

Spend the most time on the downside case. If the deal still covers its debt and preserves capital when things go wrong, the upside takes care of itself. If the deal only works in the upside case, it doesn't work.

Step 12: Review Exit Assumptions

Much of a multifamily deal's total return is realized at sale, so exit assumptions deserve real scrutiny:

• Sale year
• Exit cap rate
• Projected future NOI
• Sales costs
• Loan payoff
• Remaining investor equity
• Profit split

Example: Year 5 NOI of $1,150,000 at a 6.50% exit cap rate = $1,150,000 ÷ 0.065 = $17,692,307 sale value. Notice the exit cap rate here is higher than today's — assuming cap rates compress in your favor is one of the most common ways deals get oversold.

Common Multifamily Underwriting Mistakes

Most bad acquisitions trace back to a handful of avoidable underwriting mistakes:

• Trusting the broker pro forma — it's a marketing document, not an analysis
• Underestimating property taxes — reassessment after sale can add six figures
• Using unrealistic rent growth — 3%+ forever makes any deal pencil
• Ignoring insurance increases — premiums have jumped sharply in many markets
• Forgetting replacement reserves — roofs and HVAC don't pay for themselves
• Overstating exit value — aggressive exit cap rates manufacture paper profits
• Ignoring debt risk — rate resets and maturity walls have sunk good properties
• Not stress-testing the deal — if you never model the downside, the market will model it for you

Multifamily Underwriting Example

Here's the full deal from this guide in one place:

As-is, this deal may not be strong. The DSCR is tight at 1.12, and a 2.12% cash-on-cash return doesn't compensate investors for the risk — unless the value-add upside (closing that loss-to-lease gap, growing other income, controlling expenses) is well-supported by verified market data. That's the judgment call underwriting exists to inform.

How DealWorthIt Helps With Multifamily Underwriting

Everything in this guide can be done in a spreadsheet — slowly, and with plenty of room for formula errors. DealWorthIt is built to run this exact process end-to-end:

• Analyze multifamily deals faster
• Import T12 and rent roll documents
• Compare actuals vs projections
• Review NOI, DSCR, IRR, cash flow, ROI, and equity multiple
• Run multiple scenarios side by side
• Estimate market rents
• Review comparable properties
• Build investor-ready reports
• Stress-test assumptions before making an offer

See plans and pricing to find the tier that fits how many deals you underwrite.

Instead of spending hours trying to clean up spreadsheets, you can focus on the real question: is this deal worth it?

Frequently Asked Questions

What is multifamily underwriting?

Multifamily underwriting is the process of analyzing an apartment property's income, expenses, debt, cash flow, and projected returns to decide whether it's a sound investment at a given price. It combines verified property data (rent roll, T12) with forward-looking assumptions about rents, expenses, financing, and exit value.

What is the most important metric in multifamily underwriting?

There isn't one. NOI drives value and loan sizing, DSCR measures debt safety, and cash-on-cash return, IRR, and equity multiple describe investor returns over different time frames. Strong deals look reasonable across all of them; weak deals lean on one flattering number.

What is a good DSCR for multifamily?

Many lenders look for a DSCR of 1.20 to 1.30 or higher, depending on the property, market, and loan program. A DSCR near 1.0 means the property barely covers its mortgage — any income dip puts payments at risk.

Should I trust the seller's pro forma?

No. The pro forma and offering memorandum are sales documents built on optimistic assumptions. Underwrite from the T12, the rent roll, verified market comps, and your own quotes for taxes, insurance, and management.

What documents do I need to underwrite a multifamily deal?

At minimum: the rent roll, T12 statement, utility bills, property tax records, an insurance quote, a loan quote or term sheet, capex history, and market rent comps. The offering memorandum is useful context, but it shouldn't be your data source.

How do you know if a multifamily deal is worth it?

A deal is worth pursuing when the verified numbers — not the marketed ones — show adequate debt coverage, acceptable cash flow and returns for the risk, and a downside scenario you can survive. If the deal only works with aggressive rent growth or a compressed exit cap rate, it isn't the numbers telling you it works — it's the assumptions.

Final Takeaway

Multifamily underwriting is not about making the numbers look good. It is about finding the truth before you put real money at risk.

A strong underwriting process helps you understand the property's income, expenses, debt, cash flow, risk, and upside. More importantly, it helps you avoid deals that only work because of aggressive assumptions.

Before you make an offer, verify the numbers, run multiple scenarios, and stress-test the deal.

Want to underwrite your next multifamily deal faster? DealWorthIt helps you analyze income, expenses, debt, returns, market data, and investor scenarios in one place.