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Guides & Insights

Plain-English breakdowns of the numbers behind real estate deals — with the calculators to run them yourself.

What Is a Good Cap Rate for Rental Property?

The honest answer is "it depends" — but here are the real 2026 ranges, and how to know if a deal is actually good.

The 70% Rule for House Flipping, Explained

The one-line formula that keeps flippers from overpaying — plus when to bend it and when it will burn you.

The BRRRR Method: A Step-by-Step Guide

Buy, Rehab, Rent, Refinance, Repeat — how to recycle the same down payment into a whole portfolio, and where it goes wrong.

How Much House Can You Really Afford?

The 28/36 rule, what lenders actually check, and why the number they approve isn’t the number you should spend.

How to Get Rid of PMI (and Stop Overpaying)

The 80% request, the 78% automatic drop, and the appraisal trick that can kill PMI years early.

What Is a Good Gross Rent Multiplier?

The fastest screen in rental investing — the typical 4–12 ranges, and why the national average is useless.

The 1% Rule and 50% Rule for Rentals

Two ten-second gut-checks every landlord quotes — how they work, and why they fail in half the country.

How Mortgage Payments Actually Work

PITI, amortization, and why your early payments are almost all interest — explained in plain English.

When Does Refinancing Make Sense?

Forget the old 1% rule — in 2026 the only number that matters is your break-even point.

What Is a DSCR Loan? A Guide for Investors

The loan that qualifies your property instead of you — how DSCR works and what lenders want in 2026.

Cost Segregation Explained (and Why 2026 Is Huge)

The tax strategy that front-loads depreciation — now supercharged by permanent 100% bonus depreciation.

What Is a 1031 Exchange? The 45/180-Day Rules

How to sell an investment property and defer the capital gains tax entirely — if you hit two unforgiving deadlines.

How to Calculate Airbnb Income (ADR, Occupancy, RevPAR)

The three numbers that predict what a short-term rental will actually earn — and the 2026 benchmarks to judge them against.

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The 70% Rule for House Flipping, Explained

If you flip houses, the 70% rule is the first piece of math you should run on every deal — before you fall in love with the kitchen, before you picture the after photos. It's a guardrail that stops you from overpaying, and it takes about fifteen seconds.

The rule in one line

Never pay more than 70% of the after-repair value, minus your repair costs.

Max Offer = (ARV × 0.70) − Repair Costs

ARV is the after-repair value — what the house will sell for once it's fixed up, based on comparable sales. That's the number everything hinges on. Plug your numbers into the fix & flip calculator and it does this instantly.

A worked example

Say the ARV is $425,000 and the place needs $100,000 in repairs:

  • 70% of $425,000 = $297,500
  • Subtract $100,000 in repairs = $197,500

So $197,500 is the most you'd offer before repairs (r/FirstTimeHomeBuyer). Anything above that and you're eating into your margin.

Where does the other 30% go?

That 30% isn't pure profit — it's your buffer for everything the ARV math ignores: closing costs on both ends, holding costs (loan interest, taxes, insurance, utilities while you renovate), agent commissions when you sell, and finally your actual profit (Amerisave). The rule bakes in a cushion so a surprise doesn't wipe you out.

When flippers bend the rule

In a hot market with fast sales and reliable comps, experienced flippers sometimes stretch to 75% or even 80% of ARV. That can work — but understand you're shrinking your safety net every time you do. A single bad appraisal, a permit delay, or a $15,000 surprise behind the drywall hits a lot harder at 80% than at 70%.

The two numbers that make or break it

The 70% rule is only as good as your inputs. Get these two wrong and the whole thing falls apart:

  • ARV: Pull real, recent comparable sales — not Zillow's estimate, not what the seller "thinks." Sold, similar, nearby, recent.
  • Repair costs: Walk the property with a contractor and pad your estimate. Rehabs almost always run over, not under.

The rule doesn't guarantee a profit — it just keeps you from starting underwater. Run every potential flip through the fix & flip calculator, be honest about ARV and repairs, and walk away from the deals that don't pencil. The best flip is often the one you didn't buy.

Ready to run your own numbers?

Open the Fix & Flip Profit →
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About REI Calc

REI Calc is a free suite of 25 real estate investment calculators built for the people who actually run the numbers on deals — landlords, house flippers, short-term rental hosts, wholesalers, and buy-and-hold investors.

Why we built it

Most real estate math lives in messy spreadsheets or behind sign-up walls. We wanted a single, fast, private place to answer the questions investors ask before every deal: What's the cap rate? Does this cash-flow? Is the flip worth it at this price? How much equity can I pull with a HELOC? Every calculator gives you an instant answer and explains the formula beneath it, so you learn the math as you use it.

Who's behind it

REI Calc is run by a hands-on property investor based in Springfield, Missouri, who manages short-term and long-term rentals. The tools reflect real workflows used to evaluate, finance, and operate income properties — not textbook theory. As the site grows we're adding guides, worked examples, and market insights to help newer investors make confident, numbers-first decisions.

How it works

Everything runs in your browser. You type in your numbers, the calculator updates instantly, and nothing you enter is stored or sent anywhere. There's no account to create and no cost — the site is supported by advertising so the tools can stay free for everyone.

A note on accuracy

REI Calc provides estimates for educational purposes only and does not constitute financial, tax, legal, or investment advice. Formulas follow standard industry conventions, but real-world costs, taxes, rates, and returns vary. Always confirm your assumptions and consult a qualified professional before making a real estate decision.

Questions or feedback? Get in touch — we read every message.

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Contact us

Have a question, spotted a bug, or want to suggest a calculator we're missing? We'd love to hear from you.

Email

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[email protected]

Set up this inbox on your domain ([email protected]) so messages reach you — most registrars and email hosts let you add it in a few minutes.

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We typically reply within a couple of business days.

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Privacy Policy

Last updated: July 2026. This policy explains what information REI Calc collects, how it's used, and the choices you have.

The short version

The numbers you type into our calculators are processed entirely in your browser. We do not store, transmit, or have access to the figures you enter. We do use standard web analytics and advertising services, which are described below.

Information we collect

Calculator inputs: None are collected. All calculations run locally on your device and are never sent to our servers.

Usage data: Like most websites, we may collect anonymous, aggregated information such as pages visited, browser type, device type, referring site, and general location (country/region). This helps us understand which tools are useful and improve the site.

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This site is supported by advertising. We plan to use third-party ad networks, including Google AdSense. Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this and other websites.

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Free download

The Rental Property Deal Analyzer Checklist

The 12 numbers every investor should run before making an offer — with the exact calculator for each. Get the free PDF and occasional new-tool updates. No spam, unsubscribe anytime.