Power steering? How does it drive? Look for things like uneven tire wear, pull to one side, etc. Also, since it's steel body, you must
get low and look closely under the Jeep for damage, oil leaks, etc. Inspect for rust on frame and body mounts particularly. Take a key and poke up on the floorboards to test for integrity. If the owner won't let you do that, they can keep the Jeep. Bondo actually attracts moisture and makes rust worse
Figure to put about $1500 of mod's into it, including rust repair and deduct it from the asking price. $4200 - $1500 = $2700. There ya go!