Cash flow is the number, not the rent
The rent is the first number a seller will show you and the one that means the least on its own. What a buy-and-hold property actually produces is what is left after vacancy, every operating expense, a capital reserve, and the mortgage payment come out. That remainder is cash flow, and it decides whether a rental carries itself or quietly costs you money every month.
This post walks the stack from gross rent down to cash flow one line at a time, then shows how that final number connects to cap rate and cash-on-cash return. It uses one illustrative example with round, made-up figures. Every rate, tax, insurance, and vacancy input is a placeholder you replace with your own market and your own quotes. If your exit is BRRRR rather than a straight hold, the same stack applies after the refinance; the BRRRR calculator post covers the front half of that deal.
Start with gross scheduled rent
Gross scheduled rent is what the property would collect in a year if every unit were occupied and every tenant paid in full. It is a ceiling, not a forecast: monthly rent times twelve for a single-family, the sum of every unit's rent for a small multifamily.
Use a rent you can defend from comparable rentals, not the seller's asking rent and not a pro forma number that assumes a renovation you have not budgeted. If the property is occupied, note whether the existing lease sits above or below the rent you underwrote.
Subtract vacancy and credit loss
No rental is occupied every day of every year. Vacancy and credit loss is the allowance for turnover time and for the occasional tenant who stops paying, expressed as a percentage of gross scheduled rent. The right percentage depends on the property, the tenant pool, and how long units in that area sit between leases. Treat it as an input you research, not a constant.
Gross scheduled rent minus vacancy and credit loss is effective gross income: the money you actually expect to collect.
Every operating expense line
Operating expenses are the costs of owning and running the property regardless of how you financed it. The mortgage is not one of them; it comes later. Skipping a line here moves the cost from your analysis to your bank statement.
Property taxes and insurance
Both are knowable before you buy. Pull the actual tax bill and ask whether a sale will trigger a reassessment. Get a landlord policy quote rather than assuming the seller's premium carries over.
Property management
If you hire a manager, budget their fee as a percentage of collected rent plus any leasing or renewal fees. If you plan to self-manage, consider including the line anyway, so the analysis reflects what the property earns as an asset rather than what it pays you for your labor.
Repairs and maintenance
The ongoing items: a leaking faucet, a broken appliance, make-ready paint between tenants. It is lumpy month to month, so it is budgeted as an annual allowance, larger for older properties and for deferred maintenance.
Utilities, services, and association dues
Include anything the landlord pays rather than the tenant: water and sewer where the owner covers it, trash, common-area electric, lawn care, and any association dues. Check the current lease to see who pays what.
Net operating income
Effective gross income minus all operating expenses is net operating income, or NOI: what the property earns before financing. It is useful precisely because it ignores your loan. Two investors with different down payments and different rates see the same NOI on the same property.
Set aside a capital reserve
Separate from routine maintenance is the money set aside for large items with long lives: roof, furnace, water heater, sewer line. None shows up in a given year's bills, and all of them arrive eventually. A reserve line spreads that cost across every year of ownership. Cap rates are conventionally quoted on NOI before this reserve, so it comes out after NOI rather than among the operating expenses, but it always comes out before anything counts as cash flow. A property that only cash flows when this line is zero does not cash flow.
Debt service
Debt service is the annual total of principal and interest, set by the loan amount, the rate, and the amortization term. If your lender escrows taxes and insurance, keep those in the operating lines above and count only principal and interest here. If you acquire with short-term financing and refinance into a long-term loan, model the long-term payment for the hold; the hard money post covers what the bridge period costs.
NOI minus the capital reserve and debt service is cash flow, before income taxes. That is the line.
The worked example
All figures below are illustrative round numbers chosen to make the arithmetic easy to follow. They are not a benchmark for any market.
- Purchase price: $200,000
- Down payment: $50,000 (25%), with a $150,000 loan
- Closing costs and initial make-ready repairs: $5,000 plus $10,000
- Total cash invested: $65,000
- Loan terms assumed: 7% interest, 30-year amortization, which works out to about $998 per month, or $11,976 per year, in principal and interest
Income side, on an assumed rent of $2,000 per month:
- Gross scheduled rent: $24,000
- Vacancy and credit loss at an assumed 5%: −$1,200
- Effective gross income: $22,800
Operating expenses, each an assumed input:
- Property taxes: $2,400
- Landlord insurance: $1,200
- Management at 8% of collected rent: $1,824
- Repairs and maintenance: $1,200
- Owner-paid utilities and lawn care: $600
- Total operating expenses: $7,224
Then the bottom of the stack:
- Net operating income: $22,800 − $7,224 = $15,576
- Capital expenditure reserve: $1,200
- Debt service: $11,976
- Annual cash flow: $15,576 − $1,200 − $11,976 = $2,400, or $200 per month
Notice how much of the rent disappeared. A $2,000 rent produced $200 of cash flow, and a single line, say a tax reassessment adding $1,200 a year, would cut that in half.
How cash flow relates to cash-on-cash and cap rate
Two return metrics come straight out of the numbers above. The cap rate versus cash-on-cash post goes deeper on when to use each; here is how they connect to the stack.
Cap rate is NOI divided by price. It uses the pre-financing number, so it describes the property, not your deal. In the example: $15,576 ÷ $200,000, or about 7.8%. Because quoted cap rates are conventionally figured before capital reserves, the reserve stays out of this number; leave it in and your cap rate will not compare to the ones you see advertised. Some investors divide by total cost including closing and initial repairs instead, a figure often called yield on cost, which here gives about 7.2%; either works as long as you compare properties on the same basis.
Cash-on-cash return is annual cash flow divided by the cash you put in. It uses the post-financing number, so it describes your deal. In the example: $2,400 ÷ $65,000, or about 3.7%.
The gap between those two figures is the loan. The property earns a 7.8% cap rate, but the financing assumed here takes most of the NOI as debt service, and after the reserve that leaves a thin cash-on-cash return. Change the down payment, rate, or term and the cap rate does not move while the cash-on-cash swings widely. When a rental is advertised by its cap rate, the question is what the cash flow looks like under the financing you can actually get.
Stress-test the lines that can move
Because cash flow is a small remainder of a large number, small input errors produce large result errors. Before trusting an analysis, re-run it with each of these changed one at a time:
- Rent $100 lower than you assumed
- Vacancy doubled
- Taxes at the reassessed value rather than the seller's current bill
- Insurance at the quoted landlord premium
- The interest rate one point higher than your quote
If the deal only works with every input at its most optimistic, the deal does not work.
A rental is not a $2,000-a-month property. It is a $200-a-month property with a $2,000-a-month top line, and everything between those two numbers is where the analysis lives.
The short version
Start from a rent you can defend. Take out vacancy. List every operating expense, including the management fee you might not pay yet. That gives you NOI, which drives cap rate. Set aside the capital reserve and subtract principal and interest. That gives you cash flow, which drives cash-on-cash. Then stress the inputs that can move, because the inputs are guesses until they are quotes. Buy-and-hold is one of eight ways to exit a property; the exit strategies overview shows where it sits among the rest, and this stack is how you know whether it fits the house in front of you.
