Homes aren't just expensive to buy, they are also costly to maintain. Everything from appliances to heating and cooling systems will eventually need to be replaced.

More than 4 million Americans a year try to reduce the risk of buying home warranties, but many people wind up unhappy.

When it comes to a home warranty, experts say to do research before you buy. Get the company's complaint history from the Better Business Bureau and state department of consumer affairs, find out exactly is covered and if there is a cash option.

Experts also warn to look out for maintenance clauses. Some home warranties will only cover systems or appliances if it can be proved they've been properly maintained. If you are not the original homeowner, you may not be able to do that.