Damage to frame rails

I'm considering buying a 98 Sebring LXi but these is damage to the frame?rails to the point where the floor is slightly raised under the driver's seat.  The owner claims the damage is due to improper jacking, the rails are crushed along most of their length but there is no other underbody damage.  Does this damage compromise the integrity of the chassis or are they not an integral part of the car's structure?  Any help is appreciated.