How to Comp Multi-Family Properties

Comping a single-family home is about finding similar houses that sold nearby. Comping a multi-family property is a fundamentally different exercise. Buyers of duplexes, triplexes, quadplexes, and small apartment buildings are investors making income-based decisions. They care about rent rolls, cap rates, and NOI as much as or more than comparable sale prices.

This guide covers the methods that work for multi-family properties, from small 2-4 unit buildings to larger apartment complexes.

Why single-family comp methods fail

The standard ARV approach relies on finding similar properties that recently sold. For single-family homes, "similar" means comparable size, age, condition, and location. For multi-family, "similar" also means comparable unit count, unit mix, rental income, and operating efficiency.

A 4-unit building where each unit rents for $1,200/month is worth significantly more than an identical building where each unit rents for $800/month, even though they look the same from the outside. Income drives value for investment properties, which means you need income-based comp methods in addition to (or instead of) traditional sales comparison.

Method 1: Per-unit price comparison

The simplest multi-family comp metric is price per unit. Find recent sales of similar multi-family properties in the area and calculate the price per unit for each sale.

Example: Three recent duplex sales in the same zip code sold for $320K (2 units = $160K/unit), $290K (2 units = $145K/unit), and $340K (2 units = $170K/unit). The per-unit range is $145K-$170K, suggesting your subject duplex is worth approximately $290K-$340K.

Per-unit pricing works best when comparing properties with the same unit count. A duplex's per-unit price isn't directly comparable to a 20-unit apartment building because of economies of scale, management complexity, and buyer pool differences.

Method 2: Cap rate analysis

The capitalization rate is the standard valuation tool for income properties. It represents the expected return on investment based on the property's net operating income.

To use this method, first calculate your subject property's NOI: gross rental income minus vacancy allowance minus operating expenses (property management, maintenance, insurance, taxes, utilities paid by owner). Do not subtract mortgage payments since NOI is a pre-financing metric.

Then determine the market cap rate by finding recent multi-family sales and calculating their cap rates from publicly available or estimated income data. Apply the market cap rate to your subject's NOI to get a value estimate.

Example: Your subject generates $4,800/month ($57,600/year) in gross rent. After 8% vacancy and $18,000 in operating expenses, NOI is $34,800. Comparable multi-family sales in the area have cap rates of 6-7%. At a 6.5% cap rate, value = $34,800 / 0.065 = $535,400. Use our cap rate calculator to run these numbers quickly.

Method 3: Gross Rent Multiplier (GRM)

The GRM is a quicker, rougher version of cap rate analysis. It divides the sale price by the annual gross rent without accounting for expenses.

GRM is useful for quick screening because it doesn't require detailed expense data. But it's less precise than cap rate analysis because it ignores operating expenses, which can vary significantly between properties (a building with included utilities has higher expenses than one where tenants pay their own).

Typical GRM ranges for residential multi-family: 8-14x annual gross rent, depending on the market. Lower GRMs indicate higher returns (and often higher-risk areas). Higher GRMs indicate lower returns (and often more desirable locations).

The 2-4 unit sweet spot

Properties with 2-4 units occupy a unique position. They can be financed with residential mortgages (FHA, conventional) rather than commercial loans, which means they attract both owner-occupant buyers and investors. This dual buyer pool often pushes prices above what pure income analysis would suggest.

For 2-4 unit properties, use both traditional comp analysis and income analysis:

• Sales comparison: Find recent 2-4 unit sales in the area and compare on price per unit, condition, and location
• Income analysis: Calculate value based on cap rate and GRM
• Owner-occupant premium: If your subject is in an area where owner-occupants buy duplexes (often near colleges or in gentrifying neighborhoods), the sales comp approach may yield a higher value than pure income analysis because owner-occupants pay for lifestyle, not just returns

5+ units: income is everything

Properties with 5 or more units are classified as commercial and financed with commercial loans. Lenders underwrite based on the property's income, not the borrower's personal income. This means the property's value is almost entirely determined by its income.

For 5+ unit properties:

• Cap rate analysis is the primary valuation method
• Per-unit price is a useful secondary check
• Physical condition matters mainly because it affects rental income and operating expenses
• Location matters mainly because it affects achievable rents and vacancy rates

Unit mix adjustments

A 4-unit building with four 2-bedroom units comps differently than one with two 1-bedrooms and two 3-bedrooms. The unit mix affects total rental income, tenant turnover rates, and management complexity.

When comparing multi-family comps with different unit mixes:

• Calculate total potential income for each comp based on market rents for their specific unit types
• Compare on a gross-income basis rather than a per-unit basis
• Larger units (3-bed) typically rent for more per unit but less per square foot
• Smaller units (studios, 1-bed) have higher turnover but are easier to fill

Rent roll verification

The single most important document in multi-family analysis is the rent roll. It shows what each unit actually rents for, not what it could rent for. Current rents may be above or below market:

• Below-market rents: Create upside potential. If current rents are $800/unit and market is $1,000, there's $200/unit in upside that a buyer will pay for (partially, not fully, because raising rents takes time and some tenants will leave).
• Above-market rents: Create risk. Tenants paying above market may leave at lease renewal. Don't value the property based on above-market rents.

Always verify the rent roll against market rents. Use rental cash flow analysis to compare current rents against what the market supports.

Expense ratio benchmarks

Operating expenses for multi-family properties typically fall within predictable ranges. Use these benchmarks to validate seller-provided expense data and to estimate expenses when they're not available:

• 2-4 units (owner-managed): 30-40% of gross rent
• 2-4 units (professionally managed): 40-50% of gross rent
• 5-20 units: 40-50% of gross rent
• 20+ units: 45-55% of gross rent

If a seller claims expenses are only 20% of gross rent, they're either doing their own management and maintenance (which has value that should be accounted for) or they're underreporting expenses to inflate NOI.

Multi-family ARV for renovation projects

When evaluating a multi-family property that needs renovation, the ARV depends on the post-renovation rent increase. Calculate it in three steps:

1. Estimate post-renovation market rents (use comps of recently renovated units in the area)
2. Calculate post-renovation NOI using realistic expense assumptions
3. Apply the market cap rate to the post-renovation NOI

The renovation creates value by increasing income, which increases NOI, which increases the cap-rate-derived value. A $200/month rent increase per unit on a 4-unit building adds $9,600/year in gross income. At a 50% expense ratio and 7% cap rate, that's $68,500 in additional value from the rent increases alone.

Use the repair estimation tool to estimate renovation costs and then compare them against the value increase from higher rents.

Data sources for multi-family comps

• MLS: Good for 2-4 unit sales. Coverage drops for 5+ units.
• CoStar / LoopNet: Industry standard for commercial multi-family data (5+ units)
• County records: Sale prices for all transactions regardless of size
• Local property management companies: Can provide market rent data by unit type and neighborhood
• Apartment listing sites: Current asking rents for comparable units

Multi-family comp checklist

• Used income-based valuation (cap rate or GRM), not just sales comparison
• Verified rent roll against market rents
• Accounted for unit mix differences between comps and subject
• Validated expense ratios against benchmarks
• Used per-unit price as a secondary check
• For 2-4 units, considered both investor and owner-occupant buyer pools
• For renovation projects, calculated value increase from rent improvements

Related articles

• Cap Rate Explained
• How to Analyze a Rental Property
• Comp Adjustments: A Practical Guide
• Rental Cash Flow Analysis

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