Adjustable rate mortgages(ARM) initially come with rates lower than a fixed rate mortgage but periodically rise or fall, depending on the market. It's lower initial rate can help you qualify for a larger mortgage loan. Arm loans feature an adjustable "cap" or limitation on how much the interest can go up or down. This helps limit excessive increases in your monthly payment. If you know your income will rise to keep pace with an Arm's periodic adjustment and you plan to move in a few years, an Arm could be a good choice.