Start by reviewing sample contracts from various companies. You want a plan that covers "pre-existing conditions" not known to the seller or the agent. Pre-existing defects that are known will be excluded from coverage. Read the fine print carefully. Even though the electrical system is covered, a problem that is the result of a power outage or out-of-date wiring might be excluded from coverage. Watch out for policy limitations, such as on furnace repairs. Ideally, you will want a policy that will pay for a new furnace, if necessary, at no additional cost to you.