Rental Property Calculator
Cash flow, cap rate, cash-on-cash, and the 1% / 50% rules — all in one place.
Inputs
Purchase
Income
Operating Expenses
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Sam's Take
The number I actually look at first is monthly cash flow. Cap rate is for the brokers; cash flow is for the operators. If a deal cash-flows under $200/door/month after honest reserves, I either negotiate harder or walk. The 1% rule is a quick gut check (above 1% is rare in 2026), but it's not a substitute for running real numbers. Be honest about vacancy and maintenance — my biggest mistakes early on were pretending those would be lower than they are.
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How to know if a rental property is actually a good deal
Most "rental property calculators" online are just mortgage calculators with one extra field for rent. They tell you "income minus mortgage = profit" and call it a day. That's not how rentals work. The expenses that actually kill deals — vacancy, maintenance, capital expenditures, management — are the ones those calculators leave out. This one includes them all, with defaults pulled from a 200+ unit New England portfolio.
The five numbers that matter
- Monthly cash flow — gross rent minus PITI minus every operating expense. This is the actual money that hits your bank account. Above $200/door/month is healthy in 2026. Below $100 means one bad month wipes out the year.
- Cash-on-cash return — annual cash flow divided by the total cash you put into the deal (down payment plus closing costs plus rehab). This is your return on the dollars you actually spent. Target 8%+ on a cash-flowing rental.
- Cap rate — net operating income (rent minus operating expenses, no mortgage) divided by the price. Useful for comparing one property to another. Less useful for deciding whether to put your own money in, because it ignores how you're paying.
- The 1% rule — monthly rent divided by purchase price. Above 1% is excellent. 0.7-1% is workable in most markets in 2026. Below 0.7% means you're betting on appreciation, not cash flow. That's a bet, not an investment.
- The 50% rule — operating expenses (everything except the mortgage) tend to average about 50% of gross rent across a portfolio. If you're modeling 25% expenses on a deal, you're either missing line items or fooling yourself.
The reserves nobody puts in their spreadsheet
Maintenance and CapEx are the two most-underestimated line items in rental analysis. People skip them because they're not bills that show up every month — but they're real, and they compound over a hold period.
After 12+ years operating across New England, my actual numbers on a stabilized portfolio: 8% of gross rent for routine maintenance (toilets, drains, paint, locks, lawn care, snow), 5% for capital expenditures (roof, HVAC, appliances, kitchens, bathrooms — the big stuff that breaks every 10-25 years). Newer construction runs lower. Anything pre-1970, especially old multifamilies in New England with knob-and-tube wiring or galvanized plumbing, runs higher.
If you're penciling 3% maintenance on a 1925 triple-decker, you're going to be unpleasantly surprised in year 4. Use the real numbers. The deal either works on real numbers or it doesn't.
What "good" looks like
For a 1-4 unit residential rental with conventional 25% down financing in 2026: $200-500/door/month positive cash flow, 8-12% cash-on-cash, 6-9% cap rate. Anything significantly outside those ranges deserves a second look. Either you found a great deal — possible — or you made an arithmetic mistake. In my experience it's usually the second.