Rental Property Cash Flow Analysis

Real estate investing sounds simple: buy a property, rent it out, collect passive income. The reality involves a web of expenses that can turn a seemingly profitable deal into a monthly cash drain. Mortgage payments, property taxes, insurance, maintenance, vacancies, property management — each one takes a bite, and together they determine whether your investment actually makes money.

The good news is that rental property analysis is entirely math-based. You can run the numbers before making an offer and know with reasonable confidence whether a property will produce positive cash flow or bleed money.

Cash Flow: The Bottom Line

Monthly cash flow is the most straightforward metric: gross rental income minus all monthly expenses including the mortgage payment. If a property rents for $2,200 per month and your total monthly costs (mortgage, taxes, insurance, maintenance, management, vacancy reserve) add up to $1,900, your cash flow is $300 per month. Positive cash flow means the property pays for itself and puts money in your pocket. Negative cash flow means you're subsidizing tenants' housing.

A common mistake is forgetting to budget for vacancy. Even in hot rental markets, you'll have turnover — typically 5-10% of the year the unit sits empty between tenants. That means budgeting one month's rent per year as a vacancy reserve. Maintenance is similar: budget 1-2% of the property value annually for repairs, even if nothing breaks this year, because something will break next year.

Cap Rate and Cash-on-Cash Return

Cap rate (capitalization rate) measures the property's return based on its total value: annual net operating income divided by purchase price. A $300,000 property generating $21,000 in annual NOI has a 7% cap rate. This metric lets you compare properties regardless of financing — it strips out mortgage terms and down payment to show the property's intrinsic return.

Cash-on-cash return is what most investors actually care about, because it measures return on the money you personally invested: annual pre-tax cash flow divided by total cash invested (down payment plus closing costs plus rehab). If you put $70,000 into a deal and net $7,200 per year in cash flow, your cash-on-cash return is 10.3%. This metric accounts for leverage — using a mortgage to amplify returns on your actual capital.

The 1% Rule and When to Ignore It

The 1% rule is a quick screening tool: monthly rent should be at least 1% of the purchase price. A $200,000 property should rent for at least $2,000/month. Properties that pass the 1% test are more likely to cash-flow positively, while those well below it (say, 0.5%) almost certainly won't without exceptional circumstances.

But the 1% rule is a rough filter, not an analysis. Markets like San Francisco or New York rarely hit 1% — properties might trade at 0.4% — yet can still be good investments when factoring in appreciation. Meanwhile, a property in a declining market might hit 1.5% but carry risks that make it a poor long-term investment. Use the rule to screen quickly, then run full numbers on anything that passes.