Rust on a jeep can be anywhere, and in places you can't even see until you take it apart.

Go check out the jeep, look it over as best as you can (climb under, lift the carpets, etc.) That will give you a pretty good idea. It's good to run a magnet over the body to check for previous Bondo/bodywork. If you see bubbling coming through on the outside of the body, just remember that it's worse beneath it.

Typically, if it has excessive rust issues, you either have to be able to weld in new metal, or be willing to learn. The cost of having a bodyshop do all your bodywork will be very expensive. You can buy new $teel bodypart$, as well...

When you buy an older jeep, you have to be able to do a lot of the fixin' yourself, unless you have very deep pockets.

That's where these forums come in VERY handy.