When you say the paint is chipping "everywhere," do you mean chipping off the woodwork, the interior walls, the exterior window sills or the walls themselves?
Both inside and outside, if we're just talking woodwork/windowsills chipping, then priming the WALLS with a good sealing primer and then painting with plain old latex will seal in the lead paint there perfectly well. Then you only have to worry about maybe paying someone to do the chipping woodwork/windowsills--which will save you money. (Here where I live, people do their own "abatement"--there's no law requiring it to be done by a professional as there is with asbestos. That may or may not be true of your locale, so as you've already been advised, you need to check. Or better yet, have your attorney check--BECAUSE I KNOW YOU HAVE ONE.)
If the whole exterior is peeling, you'd have to have it scraped before you could paint anyway, so again, have a contractor take a look and give you an opinion.
If the INTERIOR WALLS are peeling and chipping, what is the extent of it?
Have you taken into consideration any of these costs in your bid?
Does your municipality or state have any special programs for lead paint abatement? Many do--it can save you a ton of money.
Do you have kids/pets or plan to anytime soon? If not, you have some time to work with your situation--just don't invite over the neighbors with the toddlers for a housewarming until everything's been done.
Who's your financer? Regular bank, FHA, VA, etc.?
Are you buying this "fixer-upper" with the intent of living in it, or becoming a landlord? (The liability possibilities here are making my head hurt.)