Is the rental actually worth it? Free, no signup.
Start with the income card: your monthly rent plus anything extra the property brings in, like laundry or parking fees. Then move to fixed costs, which means your mortgage principal and interest, monthly property tax, monthly insurance, and any HOA. The reserves card is where most back-of-the-napkin math goes wrong, so do not skip it: vacancy, maintenance, and CapEx are each entered as a percent of rent, with the placeholder hints showing the typical ranges (5 to 8 percent for vacancy, 5 to 10 for maintenance, and a steady percent for big repairs like the roof and HVAC). Add management at 10 percent if you hire it out, zero if you self-manage. If you have the deal side, enter the purchase price and your cash invested to unlock cap rate and cash-on-cash. The breakdown shows every line item, then a big monthly cash flow number, green or red. Below that, the 50 percent rule, cap rate, 1 percent rule, and cash-on-cash checks appear as you fill things in. A warning flags negative cash flow or zero reserves. No signup, runs entirely in your browser.
Example only, not typical numbers. Say the rent is $1,500 a month. You enter mortgage principal and interest of $950, property tax of $180, insurance of $90, and no HOA, with reserves of 5 percent each for vacancy, maintenance, and CapEx and zero for management. Income is $1,500. Fixed costs are $1,220. Reserves are $75 plus $75 plus $75, or $225. Total costs are $1,445, so monthly cash flow is $55, or $660 a year. Add a purchase price of $180,000 and cash invested of $40,000 and the checks kick in: the 50 percent rule compares $495 against half the income of $750; net operating income is $12,060 for a cap rate of 6.7 percent; the 1 percent rule shows rent is 0.83 percent of price; cash-on-cash is $660 over $40,000, or 1.65 percent. If that monthly number were negative, the warning would say so in red.
The tool checks it automatically: it compares your reserves plus fixed costs, excluding the mortgage, against half your gross income. It is a quick sanity check that operating costs are not eating the deal, not a guarantee the numbers work.
Take all income, then subtract the mortgage, property tax, insurance, HOA, and reserves for vacancy, maintenance, CapEx, and management. This tool subtracts each of those line by line, then shows the monthly and yearly number. This is an estimate for planning, not financial advice.
The placeholder hints suggest 5 to 8 percent of rent for vacancy and 5 to 10 percent for maintenance, with a separate CapEx percent for big repairs. These are editable starting points, not rules; an older property or a high-turnover market usually needs more.
It varies by market and property type. The tool computes net operating income divided by purchase price so you can compare deals, but a higher cap rate often means more risk or a tougher area, not a better deal.
Cash flow here subtracts the full principal and interest payment. The equity you build by paying down principal is a real benefit, but it is not cash in your pocket each month, so it does not show up in the monthly number.