How to Analyze a Rental Property: Cap Rate and Cash Flow

The Four Key Metrics

1. Cap Rate (Capitalization Rate)

Formula: Net Operating Income (NOI) ÷ Purchase Price

Example: $300,000 duplex

• Gross rent: $2,000/month = $24,000/year

• Vacancy (5%): -$1,200

• Maintenance (10% of rent): -$2,400

• Property taxes: -$3,000

• Insurance: -$600

• NOI: $16,800/year

• Cap rate: $16,800 ÷ $300,000 = 5.6%

Interpretation:

• 5.6% cap rate means property returns 5.6% annually (before mortgage)
• For comparison: 10-year Treasury is 4.2%, stock market is 8-10%
• 5.6% is okay, not great

Good cap rate zones (2026):

• Below 4%: Overpriced (avoid)
• 4-5%: Fair, depends on market appreciation
• 5-7%: Good for income
• 7-10%: Excellent cap rate (need to understand WHY it's so high—could be risky property)

2. Cash-on-Cash Return

Formula: Annual Cash Flow ÷ Down Payment

Same duplex example:

• NOI: $16,800

• Mortgage payment (80% LTV @ 6.5%, 30 years — a $240,000 loan at $1,517/month): -$18,204

• Annual cash flow: -$1,404

• Down payment: $60,000 (20%)

• Cash-on-cash return: -$1,404 ÷ $60,000 = -2.3%

Interpretation:

• You put in $60K and the property costs you about $1,400 a year to hold
• A 5.6% cap rate cannot carry a 6.5% mortgage at 80% leverage. The debt is more expensive than the asset yields, so the gap comes out of your pocket every month
• This deal reaches break-even cash flow at roughly 26% down ($78,500) and only earns a positive cash return above that
• The 5.6% cap rate did not change. Leverage is what turned a modest return into a negative one, which is exactly why cap rate alone never decides a purchase

Minimum acceptable: 3-5% cash-on-cash

3. Price-to-Rent Ratio

Formula: Purchase Price ÷ Annual Rent

Same duplex:

• Price: $300,000
• Annual rent: $24,000
• Price-to-rent: $300,000 ÷ $24,000 = 12.5

Interpretation:

• You're paying 12.5 years of rent to own it
• Below 15: Generally good (property is reasonably priced)
• Above 20: Overpriced (rent won't justify purchase)
• 15-20: Depends on local market

4. Debt Service Coverage Ratio (DSCR)

Formula: NOI ÷ Annual Debt Payments

Same duplex:

• NOI: $16,800
• Annual debt service (mortgage): $18,204
• DSCR: $16,800 ÷ $18,204 = 0.92

Interpretation:

• The property covers 92% of its own debt payments. You fund the rest
• A rent drop scales DSCR, it does not subtract from it: 30% less rent takes 0.92 to about 0.64, not to 0.62
• Minimum acceptable: 1.2 (most lenders require 1.25+)
• Ideal: 1.5+
• At 20% down this deal does not finance. A lender sizing to 1.25 allows $13,440 of annual debt service, which supports a loan of about $177,000 — a 41% down payment on a $300,000 purchase

Evaluating 5 Properties (Case Study)

Property 1: Urban Multifamily

• Price: $500K, 4-unit
• Rent: $2,200/unit = $8,800/month
• Gross rent: $8,800 × 12 = $105,600
• Vacancy: -$5,280
• Maintenance: -$10,560
• Taxes: -$5,000
• Insurance: -$2,000
• NOI: $82,760
• Cap rate: $82,760 ÷ $500K = 16.6%

Verdict: the listing is wrong, not the deal. Cap rate is a ratio, so an impossible one means an impossible input. Run the price-to-rent check on the same figures: $500,000 ÷ $105,600 = 4.7, against the 12-15 a healthy purchase shows. Nothing legitimate rents for a fifth of its price every year. Either the rent roll counts units that are vacant or below-market leases that expire, or the price excludes something — deferred maintenance, an assessment, a land lease. Get the actual signed leases and the last two years of operating statements before you believe any of these numbers.

Property 2: Suburban SFR

• Price: $350K, single family
• Rent: $2,000/month
• NOI: $20,000 (after all expenses)
• Cap rate: $20K ÷ $350K = 5.7%
• Down payment (20%): $70K
• Mortgage: $280,000 at 6.5% over 30 years = $21,237/year
• Cash-on-cash: ($20,000 - $21,237) ÷ $70,000 = -1.8%
• DSCR: 0.94

Verdict: a good asset that this financing cannot carry. The 5.7% cap rate is genuinely fine for 2026 and the property is not overpriced. But 80% leverage at 6.5% costs more than the property yields, so it bleeds about $1,200 a year and no lender underwriting to 1.25 DSCR will write the loan. It works at roughly 25% down ($86,300), where cash flow reaches break-even. Same building, different capital stack, opposite answer.

Property 3: Overpriced City

• Price: $600K, SFR in trendy city
• Rent: $2,200/month = $26,400/year
• Expenses: $8,000/year
• NOI: $18,400
• Cap rate: $18,400 ÷ $600K = 3.1%

Verdict: Overpriced. Buying for appreciation only (risky).

Property 4: Cheap Rural

• Price: $150K, duplex
• Rent: $800/unit = $1,600/month
• Expenses: $300/month
• NOI: $15,600
• Cap rate: $15,600 ÷ $150K = 10.4%

Verdict: Excellent cap rate, but understand WHY it's cheap. Crime? Bad schools? Take the 10% return if local economy is growing.

Property 5: Positive Cash Flow

• Price: $400K, 3-unit
• Rent: $2,500/unit = $7,500/month
• Expenses: $2,000/month
• NOI: $66,000/year
• Cap rate: $66K ÷ $400K = 16.5%

Verdict: same failure as Property 1, and the same test catches it. Price-to-rent is $400,000 ÷ $90,000 = 4.4, and the 16.5% cap rate trips the page's own red flag at 12%. Two independent metrics computed from the same inputs both say the inputs are unreal. When that happens, stop analyzing and go verify the source data — a spreadsheet cannot tell you a rent roll is fiction, but a ratio this far out of range always means one of the two numbers you fed it is wrong.

The Red Flags

Red flag 1: Cap rate > 12%

• Why is it so high? Market collapse? Crime area? Bad condition?
• Don't buy without understanding

Red flag 2: Cap rate < 3%

• Buying on appreciation hope only (risky)
• No income cushion

Red flag 3: Price-to-rent > 25

• Price is too high relative to rent
• Rents would need to spike 50%+ for math to work

Red flag 4: DSCR < 1.2

• Little cushion if rents drop
• Risky

Red flag 5: Vacancy assumed at 0%

• Unrealistic
• Use 5-10% vacancy assumption

The Numbers That Matter

Go, no-go decision points:

Building Your Analysis Spreadsheet

Create a simple Excel sheet:

1. Property address
2. Purchase price
3. Down payment %
4. Mortgage amount
5. Mortgage rate and term
6. Gross annual rent
7. Vacancy %
8. Maintenance %
9. Property tax
10. Insurance
11. NOI
12. Cap rate
13. Cash-on-cash return
14. DSCR

Calculate all metrics. If not in the "BUY" zone, skip property.

The 1% Rule (Quick Filter)

Rule: Monthly rent should be at least 1% of purchase price.

Example:

• Property $300K
• 1% = $3,000/month minimum rent
• If rent is $2,500, fail the test
• If rent is $3,200, pass the test

This is a rough filter. Use detailed analysis for final decision.

Sources

• NAREIA. (2026). "Rental Property Analysis Guide."
• BiggerPockets. (2026). "Cap Rate and Cash Flow Analysis."
• National Apartment Association. (2026). "Multifamily Property Metrics."
• IRS. (2026). "Rental Property Depreciation and Deductions."
• Federal Reserve Board. (2026). "Mortgage Terms and Rates."