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Rental Property Cash Flow Formula

The Core Cash Flow Formulas Every Investor Needs

Rental property cash flow analysis comes down to a few essential formulas. Mastering them allows you to evaluate any deal in minutes and avoid costly mistakes. This page covers each formula, explains the variables, and shows how they connect.

Formula 1: Net Operating Income (NOI)

NOI = Gross Rental Income – Vacancy Allowance – Operating Expenses

NOI represents the property’s profitability before financing costs. It is the starting point for nearly every investment metric including cash flow, DSCR, and cap rate.

Gross Rental Income: Total annual rent at full occupancy.
Vacancy Allowance: Typically 5% to 8% of gross rent to account for turnover and vacant periods.
Operating Expenses: All costs required to maintain and operate the property (taxes, insurance, management, maintenance, reserves).

Formula 2: Cash Flow

Cash Flow = NOI – Annual Debt Service

Debt service is the total annual mortgage payment including principal and interest. Cash flow is what remains after paying all expenses and the loan. Positive cash flow means money in your pocket. Negative cash flow means you are covering the difference.

Formula 3: Cash-on-Cash Return

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

This tells you the return on the actual dollars you put into the deal. If you invest $60,000 (down payment + closing costs) and the property produces $4,800/year in cash flow, your cash-on-cash return is 8%.

Most investors target 8% to 12% cash-on-cash return on buy-and-hold rentals.

Formula 4: DSCR

DSCR = NOI / Annual Debt Service

This formula determines whether the property qualifies for a DSCR loan. A ratio above 1.0 means the property covers the mortgage. Above 1.25 typically earns the best loan terms.

Formula 5: Cap Rate

Cap Rate = NOI / Property Value

Cap rate measures the return on the property assuming no financing. It is useful for comparing properties across markets and price points. A property with $15,000 NOI and a $250,000 value has a 6% cap rate.

Putting the Formulas Together

Here is a complete example using all five formulas:

  • Purchase price: $300,000
  • Down payment + closing: $65,000
  • Monthly rent: $2,400 ($28,800/year)
  • Vacancy (5%): $1,440
  • Operating expenses: $9,600
  • Annual debt service: $15,600

NOI: $28,800 – $1,440 – $9,600 = $17,760
Cash Flow: $17,760 – $15,600 = $2,160/year ($180/month)
Cash-on-Cash: $2,160 / $65,000 = 3.3%
DSCR: $17,760 / $15,600 = 1.14
Cap Rate: $17,760 / $300,000 = 5.9%

This property cash flows positively and qualifies for a DSCR loan, but the cash-on-cash return is below most investor thresholds, suggesting the price may be too high relative to rent.

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Frequently Asked Questions

What is the basic cash flow formula for rental property?
Cash Flow = Gross Rental Income minus Vacancy minus Operating Expenses minus Debt Service. This gives you the net monthly or annual cash flow.
What is NOI and how is it different from cash flow?
NOI (Net Operating Income) is gross income minus operating expenses, excluding mortgage payments. Cash flow subtracts the mortgage payment from NOI.
What is the 1% rule in rental property?
The 1% rule states that monthly rent should be at least 1% of the purchase price. A $200,000 property should rent for at least $2,000 per month to likely produce positive cash flow.
How do you calculate cash-on-cash return?
Divide annual pre-tax cash flow by total cash invested (down payment plus closing costs plus rehab). This shows the percentage return on your actual cash in the deal.
What vacancy rate should I use in my formula?
Use 5-8% for stable markets with strong rental demand. Use 10% or higher for markets with seasonal demand or higher tenant turnover rates.
How does property management affect the cash flow formula?
Property management typically costs 8-10% of collected rent. Include this even if self-managing to see the true cost of the investment and plan for future scaling.
What is the 50% rule?
The 50% rule estimates that operating expenses (excluding mortgage) will equal about 50% of gross rental income. It is a quick screening tool, not a replacement for detailed analysis.
How do I account for maintenance in the formula?
Budget 5-10% of gross rent for routine maintenance and another 5-10% for capital expenditure reserves depending on the age and condition of the property.
Can I improve cash flow on an existing rental?
Yes. Increase rent to market rate, reduce vacancy with better marketing, appeal property tax assessments, shop insurance annually, and reduce unnecessary expenses.
How does loan type affect the cash flow formula?
DSCR loans, conventional loans, and portfolio loans all have different rates and terms. The mortgage payment is the largest expense, so loan terms directly impact cash flow.
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