Q: A few lenders in my area recently started offering fixed-rate 40-year mortgages that they say help buyers keep their monthly payments to a minimum. This would really help me, because I want to buy a house and my budget is stretched very thin. What do you think of 40-year loans?

A: I’m not a big fan of 40-year mortgages, in part because monthly payments on the loans aren’t much lower than they’d be on a traditional 30-year plan, even though their long-term interest charges are far higher.

Banks usually charge an extra one-quarter of 1 percent on 40-year loans than they do for 30-year mortgages, because they’re exposing themselves to an extra 10 years of risk. If you were looking for a $200,000 loan today, you might be offered a 30-year repayment plan at 6 percent with monthly payments of $1,199 or a 40-year loan at 6.25 percent with payments of $1,135.

Choosing the 40-year term to lower payments by a modest $64 each month would come at a huge cost. At the end of five years, you would have paid $3,486 more in interest than you would had you chosen the 30-year plan.

And in the unlikely event that you kept the loan for its 40-year duration, your finance charges would be a staggering $113,354 more – nearly 50 percent – than you would have paid through a 30-year program.

The bottom line: If your budget is so tight that you need to stretch your loan out over an extra 10 years just to make ends meet, perhaps you shouldn’t be looking for a home right now at all. It would probably be better to wait until you can raise a bigger down payment or start earning more money to qualify for a mortgage with a shorter 30-year term.

If you’re dead-set on buying now, choosing a 30-year adjustable-rate mortgage with strict caps on how high and how fast future payment increase could occur would probably be better than getting a fixed-rate loan that will last for an extra decade.