The Jamboree is a popular model and I see a lot of them on the road. I don't have any personal experience with a Jamboree either, but can offer a couple general considerations based on age and type.
1. Check the DOT date codes on the tires to see if they are 6-7 years old. Chances are, on a 1996 motorhome with 22,000 miles, that the tires are still the originals. If so, failure is imminent regardless of how they look and you will need to purchase all new tires. Tires have a maximum life of about 7 years due to deterioration of the rubber compounds and actually die sooner if they have less than average wear. Don't let a glib salesman convince you otherwise. If you don't know how to interpret the DOT date of manufacture codes, see the Glossary of Rv Terms on www.rvforum.net, under Tire Date Codes. Basically the week and year of manufacture are encoded in the last 3 digits of the string of letters and numbers beginning with "DOT..."
2. The Ford 460 is a solid engine, as is the accompanying E4OD transmission. I had one in a previous 36 foot motorhome (also a 1996) and it performed well. The only know problem with 460's is that early models had a poor quality fuel pump that typically failed at around 30-35,000 miles. Ford changed to a better pump in mid 1996, so the one you are looking at may not have this problem.
3.Insist on operating all the appliances for substantial periods, iin both gas and electric mode. In particular, make sure the fridge cools in both modes. Fridge cooling will take several hours and perhaps even overnight
4. Check www.nadaguides.com to see the average retail price in your area. It'sa buyers market, so try to pay substantially less. RVs are usually steeply discounted, especially if you bargain HARD. In private sales, RVs usually sell closer to their wholesale value than retail.