We did that last year from a 5er to a Class C. Big thing is having wheels once you get to your camping spot. Easy for us, just drive the C over to wherever and back. Some folks need a car to tow. Another way if the camping spot is not too far away, is for one of you to drive the car and the other to drive the C to the camping spot.
The actual OP question depends on too many factors, but IMO the main one is how good you are on DIY. And DIY on what?
Eg, I am good with the RV stuff, but not on the truck type things. So I mostly didn't care about the "house" side, since I can fix all that myself mostly, but if the truck part is no good, I am helpless. That means also, I cannot tell if it any good before buying it unless I can get it to a garage I trust and get an estimate.
Generally, I agree with the above advice, if you have X dollars to spend, get a cheap RV and use the rest of the money to get it into shape. For sure, since every RV needs some work, if you blow it all on intitial cost, you will have to borrow more to get it into shape.
We are very pleased with our new to us 1991 we got last year :) It is a better floor plan etc than many new ones we have seen.
I agree about leaks! We had some, but Eternabond is your friend at $100 a roll. Not that big of a deal if you are handy.