As an example, if you borrow $250,000 at 6 percent, using a 30-year fixed-rate mortgage, your monthly payment would be $1,499. On the other hand, if you borrowed $250,000 at 6 percent, using a 30-year mortgage with a 5-year interest-only payment plan, your monthly payment initially would be $1,250. This saves you $249 per month or $2,987 a year. However, when you reach year six, your monthly payments will jump to $1,611, or $361 more per month. Hopefully, your income will have jumped accordingly to support the higher payments or you have refinanced your loan by that time.

Mortgages with interest-only payment options may save you money in the short-run, but they actually cost more over the 30-year term of the loan. However, most borrowers repay their mortgages well before the end of the full 30-year loan term.

Borrowers with sporadic incomes can benefit from interest-only mortgages. This is particularly the case if the mortgage is one that permits the borrower to pay more than interest-only. In this case, the borrower can pay interest-only during lean times and use bonuses or income spurts to pay down the principal.