Before running for the hills, I would advise giving the sellers a chance to resolve the problem - if they are willing. It is possible they first learned of the lead problem when you did, as most homeowners do not do regular water testing. It may be something as basic as an old lead water pipe that needs to be replaced.
'd start by asking your inspector if he noticed any suspicious things that could be contributing to the presence of lead. If it is well water, then filtration systems can alleviate. Many people with wells simply drink or cook with bottled water.