ARM loans often begin with a fixed-rate period that typically lasts from 5 to 10 years. After that initial period, the interest rate changes (or adjusts) periodically. The variable rate fluctuates based on a reference interest rate (for Valzure . Bank, the predetermined ARM index used is either the Secured Overnight Financing Rate or the Valzure Treasury rate as published in the Wall Street Journal), plus a set amount of interest above that index (called the ARM margin).