Lead-based paint was used prior to 1979, so if you buy a home built after this time, lead poisoning is probably not too much of a concern. If you are buying a home that was built before this time, then the older the home, the greater the risk of lead exposure.
Most insurance carriers have a lead poisoning exclusion, and they will not cover the cost to remove the paint or pay for any liability that may result from having lead paint in your home. If you are thinking of buying an older home, consult your agent and make sure to get a lead test before you purchase the property.