Real Estate, Commercial

How to Underwrite a Multifamily Property

Underwrite a multifamily property by rebuilding net operating income from the rent roll and trailing 12 months, then sizing debt to the lower of DSCR and LTV. The metrics that matter most are in-place NOI versus pro forma, debt service coverage ratio (often 1.20x to 1.25x minimum) and debt yield, tested against realistic vacancy and expense growth.

What makes multifamily underwriting different

Multifamily is the most liquid and most data-rich commercial real estate class, which makes the underwriting more about reconciliation than discovery. Value comes from hundreds of short leases that reprice every year, so income can be marked to market quickly in both directions. The core work is tying the rent roll to bank deposits, separating concessions and bad debt from headline rents, and pressure testing the expense load, especially payroll, insurance, property taxes after a sale reassessment and repairs on older systems. Risk usually hides in deferred maintenance, unit turn costs, submarket supply and a seller's pro forma that assumes renovation premiums the comps do not support.

Lenders underwrite multifamily on in-place or lightly stabilized income, apply a vacancy factor at least equal to market, add replacement reserves per unit and size the loan to the binding constraint among DSCR, LTV and debt yield. Agency and bank lenders care about durability of cash flow at today's rents. Equity investors focus on the spread between in-place rents and achievable post-renovation rents, the cost per unit to capture it, exit cap rate assumptions and IRR sensitivity to rent growth. A deal that works for equity on a value-add thesis may still be sized conservatively by the lender until the business plan is proven.

Key metrics

Debt Service Coverage Ratio (DSCR)

Shows whether in-place apartment NOI can carry the mortgage after vacancy, concessions and reserves. It is usually the binding sizing constraint on stabilized deals.

Lenders commonly look for 1.20x to 1.25x or higher on stabilized multifamily, with higher thresholds on smaller or older assets.

Net Operating Income (NOI)

Apartment value is a direct function of NOI, so the reconciled T12 and the underwriter's forward year one NOI drive both price and loan size.

Underwriters typically use the lower of trailing actuals and forward rent roll income, not seller pro forma.

Economic Occupancy

Physical occupancy can look full while concessions, bad debt and non-paying tenants erode collected income. Economic occupancy captures what actually hits the bank account.

A meaningful gap between physical and economic occupancy, often more than a few points, warrants a deeper collections review.

Operating Expense Ratio

Apartments carry heavy payroll, turnover, utilities and insurance costs. An expense ratio that looks too low usually means items are missing or deferred.

Many practitioners expect roughly 35% to 50% of effective gross income depending on vintage, utility structure and market.

Loss-to-Lease

Measures the gap between in-place rents and current market rents, which is the embedded upside or the downside if rents are above market.

Debt Yield

NOI divided by loan amount gives a leverage check independent of interest rates and cap rates, which matters when rates move quickly.

Lenders often want high single digits or better for stabilized apartments.

Breakeven Occupancy

Shows how far occupancy can fall before NOI no longer covers debt service, a direct read on downside cushion.

Lenders typically prefer breakeven occupancy comfortably below 85%.

How to underwrite it, step by step

Collect the current rent roll, T12 and bank statements, and tie collected rent to deposits month by month.
Rebuild gross potential rent unit by unit and separate loss-to-lease, concessions, vacancy and bad debt.
Normalize operating expenses, resetting property taxes to the purchase price and repricing insurance with a current quote.
Walk a sample of units and review the property condition report to size deferred maintenance and per-unit replacement reserves.
Benchmark rents and occupancy against comparable properties and new supply in the submarket.
Size the loan to the most restrictive of DSCR, LTV and debt yield at the proposed rate and amortization.
Stress the model for higher vacancy, flat rents, expense inflation and a wider exit cap rate.
Document the business plan, capex budget and reserves in the credit memo and set covenants accordingly.

Due diligence checklist

Current certified rent roll with lease start and end dates
Trailing 12 month operating statement and prior two years
Bank statements supporting rent collections
Aged receivables and delinquency report
Lease audit sample with concession detail
Property condition report and unit walk notes
Property tax bills and reassessment analysis
Insurance quotes and loss runs
Utility bills and RUBS or submetering schedule
Rent comparables and submarket supply pipeline
Capital expenditure history and renovation budget
Phase I environmental site assessment

Key risks and mitigants

Property tax reassessment after sale raises expenses well above the seller's history.

Underwrite taxes at the purchase price times the local millage rate and confirm reassessment rules with a tax consultant.

Renovation premiums in the pro forma are not supported by the market.

Size debt on in-place income, use a future funding or earn-out structure for value-add, and verify premiums against renovated comps.

Concessions and bad debt inflate reported rents.

Underwrite net effective rents and tie collections to bank deposits rather than relying on the rent roll alone.

New supply in the submarket pressures occupancy and rent growth.

Review the construction pipeline, underwrite flat or negative near-term rent growth and increase the vacancy factor.

Aging building systems such as roofs, plumbing and HVAC need near-term replacement.

Require a property condition report, fund an upfront repair escrow and set ongoing per-unit replacement reserves.

Floating rate debt becomes unaffordable if rates rise.

Require an interest rate cap, size DSCR at a stressed rate and build a debt service reserve.

Typical financing and deal structure

Stabilized multifamily is most often financed with agency debt from Fannie Mae or Freddie Mac, bank loans, life company loans or CMBS, typically on long amortization with some interest-only periods for lower leverage. Value-add deals often use floating rate bridge loans with future funding for renovations, an interest rate cap and extension tests tied to DSCR or debt yield. Small 2 to 4 unit properties are usually financed with residential or DSCR investor loans. Equity is commonly structured as a sponsor and limited partner joint venture with a preferred return and promote. Covenants usually include minimum DSCR, replacement reserve deposits, cash management triggers and restrictions on transfer and additional debt.

Red flags

Rent roll does not reconcile to bank deposits for several consecutive months.
Seller T12 shows expenses far below comparable properties with no explanation.
Large share of units on month-to-month leases or heavy recent concessions to fill vacancies.
Deferred maintenance on roofs, plumbing or electrical that the seller has not disclosed or priced.
Pro forma rent growth or renovation premiums well above what renovated comparables achieve.

Frequently asked questions

What DSCR do lenders require for a multifamily loan?

Most multifamily lenders size loans to a minimum debt service coverage ratio of roughly 1.20x to 1.25x on stabilized properties, calculated on underwritten NOI after vacancy and reserves. Smaller properties, older buildings or weaker markets often face higher thresholds. Bridge lenders may accept lower in-place coverage if there is a credible plan to reach stabilized coverage, usually backed by interest reserves and a rate cap.

How do you calculate NOI for an apartment building?

Start with gross potential rent from the rent roll, subtract vacancy, concessions, loss-to-lease and bad debt, then add other income such as parking, laundry and utility reimbursements to reach effective gross income. Subtract operating expenses including taxes, insurance, payroll, repairs, utilities and management, but not debt service or capital improvements. Most underwriters also deduct a per-unit replacement reserve.

Should you underwrite multifamily on the T12 or the rent roll?

Use both. The T12 shows actual collected income and real expenses, while the current rent roll reflects today's leases and occupancy. Lenders usually annualize the current rent roll for income if it is lower or more current, and use T12 expenses adjusted for known changes like tax reassessment and insurance renewals. Large differences between the two need to be explained before sizing the loan.

What expense ratio is normal for multifamily?

Operating expense ratios for apartments often fall somewhere between 35% and 50% of effective gross income, but they vary with building age, whether the owner pays utilities, local tax rates and insurance markets. Newer properties with tenant-paid utilities run lower, while older properties with master-metered utilities run higher. A ratio far below peers usually means missing or deferred expenses.

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Educational content, not investment, credit, legal or tax advice. Benchmarks are common practitioner rules of thumb and vary by lender, market and cycle.