Adjustable-rate mortgages

Sky's not the limit
Borrowers have some protection from extreme changes because ARMs come with caps. These caps limit the amount by which ARM rates and payments can adjust.

Caps come in a couple of different forms. The most common are:

Interest-only ARMs
Around the turn of the 21st century, lenders began to market interest-only mortgages to middle-class borrowers. Formerly the preserve of what lenders called "affluent clients," interest-only mortgages are usually adjustables. The borrower is required to pay only the interest for a specified period, often 10 years. After that, it adjusts to the going interest rate, as tracked by a specified index. After that, the loan amortizes at an accelerated rate. During the interest-only period, the borrower can choose to pay some principal, too. By providing flexibility in the size of monthly payments, interest-only mortgages often are a good match for people with fluctuating monthly incomes: salespeople who are paid by commission, for example.

Variety of flavors
Some ARMs come with a conversion feature that allows borrowers to convert their loans to fixed-rate mortgages for a fee. Others allow borrowers to make interest-only payments for a portion of their loan terms to keep their payments low. But no matter the exact terms, most ARMs are more difficult to understand than fixed-rate loans.

To keep your financial options open, make sure to ask the mortgage lender if the ARM is convertible to a fixed-rate mortgage. Also, ask if the ARM is assumable, which means when you sell your home the buyer may qualify to assume your existing mortgage. That could be desirable if mortgage interest rates are high.

Bankrate.com also surveys ARM interest rates.