Keep your $600 and run, you are looking at a lot of $$$ to get that thing into shape to run and this guy knows it is shot and is trying to unload it on someone who is not too bright, $600 is probably double what he would get for it at a junk yard, if they would even pay anything for it.
Question is are you looking to travel or to park for some time?
If you are going to just be setting in one place, you will get more bang for your buck by getting a travel trailer (tt) or a 5th wheel (5er).
If you are planning to follow the seasons and travel then look at the motor homes. In either case you can get a cheap car, either to tow behind the mh or to drive to work.
BTW, welcome to the group.