I've noticed something strange about mortgage pre-approvals. A buyer walks into a lender's office wondering whether he can afford a house. The lender looks at his income, debts, credit history, and financial obligations, runs the numbers, and announces: "Congratulations! You qualify for $600,000." And somehow, the buyer hears: "Congratulations! You should buy a $600,000 house."

That's a remarkable leap of logic. If my doctor told me I could survive eating fourteen cheeseburgers, I wouldn't immediately order fourteen cheeseburgers. Well, maybe thirteen. I'm not an irresponsible man.

But a mortgage pre-approval has a peculiar psychological effect. A number that was supposed to establish a borrowing limit suddenly becomes a shopping target. And I say this as someone in the lending business: when did the maximum amount someone is willing to lend you become the amount you should want to borrow?

Of course, lenders don't simply invent these numbers. Debt-to-income ratios, credit scores, down payments, and underwriting guidelines exist for good reasons. And borrowing near your approved limit isn't automatically reckless. A buyer with substantial savings, stable income, and good prospects may have perfectly sensible reasons to do it. But here's the distinction that bothers me. A lender is trying to determine whether a loan represents an acceptable risk under its lending criteria. A borrower should be asking whether the payments represent an acceptable way to live. Those aren't quite the same question.

The lender doesn't necessarily know how much you value vacations, whether you're planning to have children, how much you help your parents, or whether you'd rather spend your weekends playing guitar than worrying about the next property tax bill. And the lender certainly isn't promising that the next thirty years will be comfortable. Yet I've seen how easily a financial ceiling can start looking like a personal achievement.

Maybe the problem isn't that lenders approve people for too much. Maybe it's that we've started treating borrowing capacity as purchasing advice. A pre-approval tells you what you may be able to buy. It doesn't tell you what you ought to buy.

So here's my question: If a bank approves you for $600,000 and you buy a $450,000 house instead, have you missed an opportunity - or made a decision the bank was never qualified to make for you?