The choice between a 15-year and a 30-year mortgage is really a choice between a lower payment and a lower total cost. Both are valid, and the right answer depends on your budget and your goals more than on any rule.
The 30-year case
A 30-year loan spreads the balance over more payments, so each one is smaller. That lower payment buys breathing room, easier qualification, and cash left over for saving, investing, or simply living. The trade-off is that you pay interest for twice as long, so the total interest is much higher.
The 15-year case
A 15-year loan carries a higher monthly payment because you are repaying the same balance in half the time. In return you usually get a lower interest rate and you pay dramatically less interest overall, often less than half. You also own the home outright far sooner.
See the numbers
The gap is easiest to feel with real figures. Take a loan to our calculator, note the total interest at 30 years, then switch the term to 15 years and watch it fall. For many loans the 15-year total interest is under half the 30-year figure, even though the monthly payment is only about 40% to 50% higher.
A middle path
You do not have to pick the extremes. Taking a 30-year loan and paying extra each month gives you the flexibility of the lower required payment with much of the interest saving of a shorter term. If your income is steady and you value certainty, the 15-year commitment can be worth it. If it is variable, the 30-year with voluntary extra payments is often the safer choice.