Real Estate Math

The 1% rule says monthly rent should equal 1% of purchase price. See what the screen catches, what it misses, and why my duplex failed it and still won.

Cap rate is net operating income divided by purchase price. See the formula, a line-by-line duplex example, and why house hackers need a different metric.

Identification is a filtering job, not a treasure hunt. The four screens, in the order that kills bad deals cheapest.

The metros where owning a duplex beats renting, ranked by what you keep each month, with the full math, the assumptions and the sources behind every figure.

Five ten-second screens for rental deals: the 1% rule, 50% rule, cap rate, cash-on-cash and the 70% rule, each explained with a free calculator to run it.

Twelve more metros through the same conservative duplex math at 2026 rates, priced from every active listing: two clear the bar, two cost about the same as renting, and eight cost more to own.

Five free house hacking calculators compared: what each one does well, where each falls short, and how to use them together on a real two-to-four-unit deal.

The ranges investors actually target, how the number compares to stocks and bonds, and why house hackers should read the benchmarks differently.

Which expenses house hackers can deduct on an owner-occupied duplex, how the unit split works, and where depreciation fits. Based on IRS Pub 527.

The full walkthrough I run on a listing before deciding whether to write an offer, from the first gut check to the red flags that kill a deal.