Finance

Buy a house

The asking price is not the number that matters. Four tools turn it into a monthly payment, a break-even year, and an honest answer to whether buying beats renting.

4 steps 7 min read 4 tools chained Money

Start with what it actually costs each month

A $400,000 home with 20% down is a $320,000 loan. At 6.5% over 30 years the principal and interest alone come to the figure below — before tax, insurance or any association fee, all of which the tool adds separately.

Monthly P&I$2,023
Interest over 30 years$408,142
If the rate were 7.5%+$215/mo
Rule of thumbEvery 1% on the rate moves your buying power about 10%. Rate beats price when you are deciding what to offer.

Now ask whether buying wins at all

Owning is not automatically better. The money you would have put down can be invested instead, and transaction costs are front-loaded — sell too early and renting was cheaper. Rent vs Buy finds the year the lines cross.

Compared over7 years
Rent assumed$2,200/mo
Invested instead at7%/yr
Rule of thumb"Rent is throwing money away" ignores what the deposit would have earned. Compare total wealth at the end, not monthly outgoings.

Put the deposit somewhere and watch it work

Whether you buy or not, the same engine governs the savings. A $10,000 start plus $200 a month at 7% for twenty years is the standard yardstick — and it shows how little of the final figure you actually paid in.

Becomes$144,573
You paid in$58,000
Growth did the rest$86,573
Rule of thumbRule of 72: divide 72 by the rate to get the doubling time. At 7%, money doubles roughly every ten years.

Check the whole thing against a real income

Lenders think in ratios, and so should you. Put your actual pay in and compare the monthly payment against take-home rather than gross — the gap between the two is where budgets quietly fail.

28/36 rulehousing ≤28% of gross
All debt≤36% of gross
Rule of thumb28/36: housing under 28% of gross income, total debt under 36%. Above that, the arithmetic works but the month does not.

You went from a sticker price to a decision

Four tools, one thread: what it costs monthly, whether owning beats renting over your actual horizon, what the deposit would have done instead, and whether your income carries it. Change any single input and walk the chain again — that is the point of it.

Reference only. Stories chain real tools — the numbers shown are worked examples, so check them against your own figures before relying on them.