I Ran the Numbers and Barely Made Money. That’s Not a Bug.

Run a handful of realistic rental scenarios through this calculator and you’ll probably land somewhere similar to where I did testing it: thin cash flow, sometimes barely positive, sometimes not. If that surprises you, it should, and it’s worth understanding why, because that surprise is exactly the point of this tool existing.

Short version: This calculator runs cash flow, cap rate, cash-on-cash return, and the 1% rule using honest, current 2026 assumptions, not the optimistic defaults you’ll find on plenty of real estate portals and listing sites, which have a real incentive to make a deal look better than it actually is. Rental margins genuinely are thin right now, investment property mortgage rates running 7.3-7.8% and home prices having outpaced rents for years. Thin isn’t the same as bad, appreciation and equity are still doing real work even when monthly cash flow barely clears zero, which is exactly why the optional market-comparison toggle exists.

Why This Calculator Won’t Make You Feel Better About a Bad Deal

A lot of rental property calculators floating around real estate listing sites and “turnkey rental” sellers exist for a reason that has nothing to do with giving you an honest answer, they’re built to get you to click “get pre-approved” or “talk to an agent.” That’s not a conspiracy theory, it’s just how the incentives work: a calculator that shows weak cash flow doesn’t convert nearly as well as one that shows a comfortable green number. So the defaults quietly lean optimistic, low vacancy assumptions, no property management fee (because you’ll obviously self-manage and never get tired of 2am maintenance calls), no CapEx reserve, aggressive rent growth.

This one doesn’t have that incentive. Nobody’s paying to have a deal look good here. The default assumptions, 5% vacancy, a real property management line, a genuine CapEx reserve, current investment-property mortgage rates instead of primary-residence rates, are the same categories a serious investor would actually underwrite with, not the version built to get you excited enough to fill out a lead form.

The Four Numbers That Actually Matter

Monthly cash flow is what's actually left over every month after every real expense, including the mortgage. This is the number that pays your bills if something breaks.

Cap rate measures the property's return as if you'd paid all cash, no mortgage involved at all. It's how you compare two completely different properties, different price, different financing, on the same basis.

Cash-on-cash return is the number leveraged investors actually care about most: your annual cash flow divided by the actual cash you put in, down payment, closing costs, rehab. This is the metric a small deposit and a big mortgage can genuinely boost, and also the one that shows exactly how thin the margin is once real financing costs are included.

The 1% rule is a fast screening filter, monthly rent divided by total acquisition cost. It's not an analysis. It's a first pass to decide whether a property is even worth running the full numbers on.

Why Cap Rate Excludes CapEx (and Why That Trips People Up)

Here's a detail that even DIY spreadsheets get wrong constantly: net operating income, the number cap rate and DSCR are both built on, excludes capital expenditures entirely. Not because CapEx doesn't matter, it absolutely does, but because NOI is meant to measure how a property performs on its own, independent of financing and independent of large one-time costs that vary wildly by property and by year. CapEx only shows up further down, when calculating actual cash flow, alongside the mortgage payment. Skip this distinction and your cap rate ends up understated and not comparable to how any real lender, appraiser, or investor would calculate it. This calculator keeps that separation exactly where industry practice puts it.

The 1% Rule in 2026: The Honest Version

You've probably heard the 1% rule stated as a settled fact. It's worth knowing where it actually stands right now. Nationally, it's genuinely difficult to clear, the median home price sits around $400,000, which would require roughly $4,000 a month in rent to hit 1%, while median rent nationally runs closer to $2,000. Home prices have simply outpaced rents for years. That said, it's still realistic in more affordable markets, places like Cleveland, Memphis, Kansas City, and Indianapolis still produce properties that clear it. A property that misses 1% isn't automatically a bad deal, and one that clears it isn't automatically a good one, current financing costs mean a property that technically passes can still be cash-flow negative once real expenses are included. Treat it as a starting filter, never a verdict.

Rental Income Isn't Self-Employment Income

Worth naming directly, since it's an easy assumption to make and it's genuinely wrong most of the time: rental income doesn't work like income from a trade business. Trade income typically goes on Schedule C and is subject to self-employment tax, that 15.3% on top of regular income tax covered elsewhere on this site. Rental income typically goes on Schedule E instead, and in most cases isn't subject to self-employment tax at all, since the IRS generally treats it as passive income rather than earnings from a trade or business you're actively running. That's a genuinely different tax mechanism, not a minor technicality, and it's exactly the kind of thing worth getting right before assuming your rental numbers work the same way your business numbers do.

The Optional Toggles

Rent growth and appreciation are both off by default, deliberately conservative, same logic as the rent vs. buy calculator. Turn them on to see how the picture changes over a real holding period rather than a single snapshot year.

Comparing to the market instead takes your actual cash invested and grows it at a return rate you choose, then measures it against the property's real total return, cash flow collected plus equity built. This is the toggle that usually explains why real investors put up with thin monthly cash flow in the first place: leverage means you're capturing 100% of the appreciation on a property you only put 20-25% down on, which can outpace an unleveraged market return even when the monthly number barely clears zero. Same caveat as always: past market returns aren't a promise, and neither is property appreciation.

Once You're Past One or Two Properties

This calculator is built for evaluating a single property, the numbers a first-time buyer actually needs. Once someone's running several properties through an LLC, possibly with a property manager on payroll, the questions genuinely shift, entity structure, separate banking, and potentially the same 1099-vs-W-2 classification question that applies to hiring in any trade business. That's a different set of decisions than this tool answers, covered starting with going independent and business banking and bookkeeping once it's actually relevant.

Where to Go From Here

If you're deciding whether rental property fits your bigger financial picture, rental income as passive income covers that ground more broadly, and short-term rentals walks through the Airbnb and VRBO side specifically if that's the model you're considering instead. Once you've got a specific property and a specific rate in mind, the mortgage calculator and house affordability calculator help confirm the financing side holds up too.

Sources

• https://www.reit.com/glossary/net-operating-income
• https://janover.pro/glossary/noi
• https://www.commercialcafe.com/blog/1-percent-rule-real-estate-investing/
• https://fourcasa.com/blogs/the-1-percent-rule-does-it-still-work-in-2026
• https://themortgagereports.com/27698/investment-property-mortgage-rates-how-much-more-will-you-pay
• https://www.irs.gov/taxtopics/tc414