These loans generally begin with an interest rate that is 2-3 percent below a comparable fixed rate mortgage, and could allow you to buy a more expensive home.

However, the interest rate changes at specified intervals (for example, every year) depending on changing market conditions; if interest rates go up, your monthly mortgage payment will go up, too. However, if rates go down, your mortgage payment will drop also.

There are also mortgages that combine aspects of fixed and adjustable rate mortgages - starting at a low fixed rate for seven to ten years, for example, then adjusting to market conditions. Ask your mortgage professional about these and other special kinds of mortgages that fit your specific financial situation.

Choosing an ARM with an index that reacts quickly lets you take full advantage of falling interest rates.

A few options are available to fit your individual needs and your risk tolerance with the various market instruments.

ARMs with different indexes are available for both purchases and refinances. Choosing an ARM with an index that reacts quickly lets you take full advantage of falling interest rates. An index that lags behind the market lets you take advantage of lower rates after market rates have started to adjust upward.

The interest rate and monthly payment can change based on adjustments to the index rate.

6-Month Certificate of Deposit (CD) ARM
This program has a maximum interest rate adjustment of 1% every six months. The 6-month Certificate of Deposit (CD) index is generally considered to react quickly to changes in the market.

1-Year Treasury Spot ARM
This program has a maximum interest rate adjustment of 2% every 12 months. The 1-Year Treasury Spot index generally reacts more slowly than the CD index, but more quickly than the Treasury Average index.

6-Month Treasury Average ARM
This program has a maximum interest rate adjustment of 1% every six months. The Treasury Average index generally reacts more slowly in fluctuating markets so adjustments in the ARM interest rate will lag behind some other market indicators.