Rental Cash Flow and Cap Rate: A Simple Guide for Landlords

Whether you are buying your next rental or checking how your current one performs, a few numbers tell you most of what you need. Cash flow tells you what lands in your pocket. Cap rate lets you compare properties on equal footing. This guide walks through both with simple round numbers. Your own figures will differ, so treat the example as a template.

Start with the building, not the loan

The first step is to look at what the property earns before financing. That keeps the analysis clean, because two buyers can buy the same building with different loans and the building itself should be judged the same.

Net operating income (NOI) is the money the property generates after operating expenses but before mortgage payments and income taxes.

NOI = rent collected - operating expenses

Operating expenses typically include:

• Property taxes
• Landlord insurance (see landlord insurance explained)
• Repairs and routine maintenance
• Property management fees, if you pay them
• Utilities you cover
• Advertising, software, and professional fees
• A line for vacancy and an allowance for big-ticket items

What is not in operating expenses: mortgage principal and interest, income taxes, and depreciation. Depreciation is a tax deduction, not a cash cost, so it does not belong in your cash flow math.

What cap rate tells you

Capitalization rate is a quick measure of a property’s return if you bought it with cash:

Cap rate = NOI / purchase price

If a property produces $14,000 of NOI and costs $200,000, the cap rate is 7%. A higher cap rate means more income per dollar of price, but it often comes with more risk, older buildings, or weaker locations. A lower cap rate may reflect a stronger area or more stable demand. Compare cap rates only between similar properties in similar places.

Cap rate has limits. It ignores your loan, it relies on the expense numbers you feed it, and it says nothing about future rent growth or big repairs. Treat it as a screening tool, not a verdict.

Cash flow and cash-on-cash return

Cash flow is what is left after debt service:

Cash flow = NOI - mortgage payments (principal and interest)

Cash-on-cash return compares annual cash flow to the cash you actually put in, including the down payment, closing costs, and any upfront repairs:

Cash-on-cash = annual cash flow / total cash invested

Cash-on-cash matters because most landlords borrow. The same property can have a modest cap rate but a decent cash-on-cash return, or the reverse, depending on the interest rate and how much you put down.

A worked example

Here is a hypothetical single-family rental. All numbers are round and for illustration only.

With a $200,000 price:

• Cap rate: $14,000 / $200,000 = 7%
• Monthly cash flow: $3,200 / 12, about $267
• Cash-on-cash: if you invested $50,000 total, $3,200 / $50,000 = 6.4%

Notice how thin that monthly cash flow is. A single $3,000 repair would wipe out nearly a year of it, which is why reserves matter. This simplified example also has no separate capital expense reserve; adding one, as recommended above, would lower NOI, cap rate, and cash flow further.

Stress-test the numbers

Before you rely on a result, change the inputs and see what breaks:

1. Raise vacancy to two months a year instead of a few weeks.
2. Raise repairs by 25% to 50%, especially for older properties.
3. Raise insurance and tax estimates, since both can climb after a purchase or reassessment. Check how your county reassesses taxes after a sale.
4. Lower rent to the low end of comparable listings.
5. Raise your interest rate if you have an adjustable loan or plan to refinance.

If cash flow stays positive under a few of these, the deal has some cushion. If it turns negative quickly, you are depending on everything going right. Your starting rent should come from comparable listings, not hope; see how to set a rental price. If your area limits increases, plan for slower income growth as explained in rent control explained.

Pre-tax vs. after-tax

Everything above is before income taxes. Real take-home income can differ because interest and depreciation reduce taxable income, while principal payments do not. A property can show positive cash flow but a small taxable loss on paper, or the reverse. See rental property depreciation explained and landlord tax deductions for how these items affect your return, and confirm specifics with a CPA.

Common mistakes

1. Using the seller’s expense numbers without checking them against tax bills and insurance quotes
2. Leaving out management costs because you plan to do the work yourself, even though your time has value
3. Counting principal payments as an expense, or forgetting that they build equity but not cash flow
4. Comparing cap rates across very different markets or property types
5. Forgetting upfront repair costs in cash-on-cash calculations

Next steps

Pick one property and build a one-page worksheet with the lines from the table above, using real bills from the last 12 months. Calculate NOI, cap rate, cash flow, and cash-on-cash, then run the stress tests. If you are comparing a possible purchase, repeat the process for two or three alternatives so you are judging on the same basis. Keep the worksheet with your rental records and update it every year.

Related guides

• Short-Term vs Long-Term Rental: Which Is Right for Your Property?