You can save some money when you get a mortgage with an adjustable interest rate, especially when rates are low. This option also is helpful for providing more breathing room when you need a Jumbo Loan. Here’s how ARMs work: You get a fixed rate for a few years before the mortgage adjusts annually, based on a particular index value. Point is, you either want to sell before your rate increases or refinance your mortgage. But you’ll save money upfront because the intro rate is lower than a fixed-rate option.