Today the interest rates charged on fixed-rate mortgages are almost the lowest they have been in two decades. That's good news for potential home buyers.

Even better news is the fact that the interest charged on some Adjustable Rate Mortgages (ARMs) is at a level not seen in four decades.

However, you should be cautious if you choose an ARM First, keep in mind that the ridiculously low rates offered on ARMs usually are guaranteed just for the first year.

You should also be aware that, because of the potential for volatility, lenders will usually require that you qualify for a mortgage loan several percentage points above the actual initial rate charged on the ARM.

This is intended to eliminate marginal borrowers from becoming overburdened by debt.

You should also be on the alert for lenders who charge special fees or caps that can increase the cost of the loan to you.