First, like everyone said, you have no responsibility for it since you sold it as is.
Second, because it was on a lift, it could inturn be the possibility that the lift operator should have checked the car before lifting it since he could have been endangering the people where he works. So he would be partially at fault.
With the Frame, since the car is Unibody, you'll have a hard time just welding in a new piece. And depending on how bad it was mangled by the lift, it probably isn't worth the effort. It'd be more than the car is worth.
I personnally purchased a 93 SSE SC knowing it had a little rust in the quarters. When I got it home, I realized that it had a lot more, including a 6 inch hole under the rear seat. Did the owner know about it? No. Could the same thing have happened if I put it on a lift? Yes. Did I go back? no, cause I knew I didn't look there. For me, I bought it for parts so it was fine, but it is the same deal.There was a lot of unforseen stuff
2007 Saturn Aura XR | 1970 Chevy Blazer 4x4 | 1970 GMC 3/4 Suburban 4x4