They are unibody so structural rust is a killer. Especially bad areas are the rear strut towers(viewable through the trunk), frame rails, drivers floor, front fenders, rear subframe mounting points and rockers. Unless you are a sadist or a bodyman avoid cars with some combination of these issues, especially rear shock towers. Mechanicals can be fixed, but if the body is crap, you are in real deep. Take your magnet, flashlight and screwdriver. Spend some time on
www.2002faq.com as well.