An adjustable rate mortgage (ARM) is a type of loan for which the interest rate can change, usually in relation to an index interest rate. Your monthly payment will go up or down depending on the loan’s introductory period, rate caps, and the index interest rate. With an ARM, the interest rate and monthly payment may start out lower than for a fixed-rate mortgage, but both the interest rate and monthly payment can increase substantially.
Your monthly payments are more likely to be stable with a fixed-rate loan, so you might prefer this option if you value certainty about your loan costs over the long term. With a fixed-rate loan, your interest rate and monthly principal and interest payment will stay the same. Your total monthly payment can still change — for example, if your property taxes, homeowner’s insurance, or mortgage insurance might go up or down.
Adjustable-rate mortgages (ARMs) offer less predictability but may be cheaper in the short term. You may want to consider this option if, for example, you plan to move again within the initial fixed period of an ARM. In this case, future rate adjustments may not affect you. However, if you end up staying in your house longer than expected, you may end up paying a lot more. In the later years of an ARM, your interest rate changes based on the market, and your monthly principal and interest payment could go up a lot, even double.
(Source: Consumer Financial Protection Bureau)
