How does cash flow work on a rental property?

Cash flow is what is left over after you collect the rent and subtract vacancy, the mortgage, taxes, insurance, and maintenance. It is the money the rental puts in your pocket each month, and it is the most direct measure of whether a property pays for itself. Positive cash flow means the property funds its own costs; negative cash flow means you cover the gap.

Every expense that touches the property belongs in the calculation, from the big items like the mortgage and taxes to the recurring ones like maintenance and management. The accuracy of the estimate determines the value of the answer.

The income side starts with the gross rent, then is reduced for vacancy to reflect reality. No property collects rent every single month, and a realistic vacancy allowance is essential. Any other income, like parking fees or laundry, adds to the gross, but keep the projections conservative.

The key discipline is not overstating the rent. Use comparable rents and a vacancy allowance, and the income number becomes a figure you can build a decision on.

On the expense side sit the mortgage, property taxes, insurance, maintenance, and any property management fees. The mortgage is often the largest line, and taxes and insurance are fixed costs that vary by property and area. Maintenance is the variable that surprises new landlords, so a monthly reserve for repairs belongs in the budget.

Add up every recurring cost and a share of the big ones, like a new roof or HVAC that will eventually arrive. A cash flow projection that skips maintenance is a projection that lies to you.

Cash flow measures the monthly income, but the full return also includes principal paydown and appreciation. A property that breaks even on cash flow can still be building wealth as the tenants pay down the mortgage and the home appreciates. That is why investors look at cash flow, cash-on-cash return, and total return together.

Still, negative cash flow deserves scrutiny, because you are funding the difference from your own pocket every month. Many investors accept modest or even negative cash flow in the early years when the long-term growth justifies it, but only with eyes open.