What Is the 3-3-3 Rule for Buying a House?

The 3-3-3 rule is an informal affordability check, not a lending standard. The most common version says to keep the purchase price at or below three times your gross annual income, put at least 3% down, and hold three months of expenses in reserve after closing. It is a useful gut check, but in Greater Boston one of the three pieces rarely survives contact with the market.

What Each 3 Actually Means

Three times income. As an illustration, a household earning $150,000 a year would cap its price at $450,000. The logic is sound: a price-to-income ratio that low leaves room for taxes, insurance, repairs and life.

3% down. Many conventional loan programs accept this minimum, and FHA loans sit just above it. It does not cover closing costs, which in Massachusetts are a separate check you write at the closing table.

Three months of reserves. The cash you still have after the down payment and closing costs should carry your mortgage and core bills if income stops or the boiler fails in January.

You will see other versions online, some swapping in a three-year minimum stay. The idea is the same: buy with a cushion, not on the edge.

How It Holds Up Near Boston

The three-times-income cap is the part that breaks. In many towns around Boston, prices run well above three times what most local households earn, so a strict reading would rule out most of the market. You can compare incomes and housing figures by town with the town data explorer.

Lenders do not use this rule anyway. They underwrite to your debt-to-income ratio, where the new mortgage payment counts alongside your car loan, student loans and card minimums. That is why two buyers with the same salary can be approved for very different amounts.

The other two 3s hold up better. In my experience, the buyers who struggle in the first year are rarely the ones who bought at four times income with healthy reserves. They are the ones who emptied their savings to close and then met a roof leak or a sewer line repair with nothing left.

A Better Way to Use It

Treat the rule as a starting conversation, not a verdict. If you exceed three times income, ask what you are giving up: retirement contributions, travel, a cushion for job changes. If the answer is uncomfortable, the price is too high regardless of what a lender approves.

Run your real monthly payment, including property taxes and insurance, before you shop. Then protect the reserve number even if it means a smaller down payment.

Bottom Line

The 3-3-3 rule is a decent sanity check but a poor fit for Greater Boston prices on its own. Lean on the down payment and reserve pieces, and judge price by the monthly payment you can carry comfortably. If you want to test a few scenarios, the mortgage calculator is here.

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Plato Asadov (Aflatun Asadov)
Licensed Massachusetts Real Estate Salesperson, Lic. #9579004
Brokered by Steve Bremis Realty Group. Equal Housing Opportunity.
Phone: 617-302-7222 · Email: plato@realestoria.com · realestoria.com
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This article was drafted with AI assistance from Plato's research tools and reviewed by Plato before publishing. Information deemed reliable but not guaranteed; it is general education, not advice for your specific situation.