Common problems but almost unavoidable are:
Rust in the bottom of rear quarters
Rust in spare tire well
Rust in rear quarter to trunk floor extensions
Rust in interior floor pans
A little less common but repairable:
Rust in bottom of front fender
Rust in top of front fender (above tire)
Rust in bottom of doors
Rust in sill panels, below doors.
Serious rust problems, these can be repaired but at considerable PIA factor:
Rust in rear window channels
Rust in lower front window channels
Rust in Rear frame rails
Rust in torsion bar mounts
If you are not an experienced Mopar guy, I would definately take someone along with you to check out the car.