When you buy a house, the mortgage company wants to make sure it won't be hurt too badly if you skip town without paying off the loan. Unless you can put down at least 20% of the home's value, you're usually required to get PMI. The policy's purpose is mainly to secure the lender's investment, but in recent years it's become a means for people to buy a home with a much smaller down payment.

But homeowners pay for it in the long run. Premiums can amount to as much as a 13th mortgage payment each year.

Once the outstanding balance on your mortgage drops below 80% of the original value of the home, federal law says your lender must notify you that you can cancel the insurance. As unlikely as it may be in the current housing market, if your home has appreciated rapidly, you can also apply to cancel PMI. But be prepared to pay for an appraisal ($300 to $400) to prove your point.