Real estate math you can check yourself.

Net operating income as a percentage of purchase price — the standard first-pass measure of what a rental earns before financing, with every step shown.

Itemize income and operating expenses line by line to get a property's net operating income — the number cap rates and appraisals are built on.

Annual pre-tax cash flow after the mortgage, as a percentage of the cash you actually invested — cap rate's levered counterpart.

The full monthly pro-forma — gross rent through vacancy, operating expenses, and the mortgage to the cash in your pocket, monthly and annual, with every line shown.

Debt service coverage ratio — net operating income divided by debt service, the number rental and DSCR-loan lenders use to size a loan, with common thresholds shown.

After-repair value from comparable sales — each comp's price per square foot, averaged and applied to your square footage, with every step shown.

The flipper's maximum offer — after-repair value × 70% minus repair costs — with the rule percentage yours to adjust for your market.

The full accounting of a flip — purchase, rehab, holding, and selling costs against the expected sale price, with projected profit and return on cost.

Build a flip's repair budget the honest way — a line-item takeoff of the scope of work by category plus a contingency, producing the repair-costs figure the 70% rule and flip profit tools ask for.

Buy, rehab, rent, refinance — how much of your capital the cash-out refinance pulls back out, the rental cash flow after the new loan, equity, and cash-on-cash.

Monthly principal & interest from price, rate, and term — plus taxes, insurance, and HOA — with the amortization formula shown.

Compare your current loan to a new one — monthly saving, the break-even point on closing costs, and lifetime interest — so a lower rate that quietly costs more can't hide.

The full payoff table — how every payment splits between principal and interest, the balance year by year, and how extra payments cut interest and shorten the loan.

Compares the full net cost of buying against renting over your holding period — appreciation and equity against the opportunity cost of your down payment — so a fair answer replaces the “rent is throwing money away” myth.