I wouldn't say the used RV market is "extremely limited" by any means, but that probably depends a lot on your area. Start shopping Craigslist and Ebay ads to get an idea of what's out there. Ebay can show you what things are actually selling for.
I'd agree with what Richard said about a 1997 or up F53. For perspective, I sold my 1994 Thor Residency (35-foot Class A) in 2012 for $8000. It did not need any immediate expensive maintenance items, but it was definitely used. Worked great for the guy I sold it to though, so there is a buyer and a seller for every type of rig. You can find 1980's models for $5000-6000 in good running condition sometimes. It really depends on what you are wanting and your planned uses of the rig.
It's also important to note that all RV's (used or new) will need ongoing tinkering and maintenance... it's just the nature of the beast. If you have $10,000 max then you probably should only spend $8500-9000 on the RV itself, to allow a cushion for unanticipated repairs. That's assuming it is purchased in drive-away condition. High dollar items to verify on used RV's are the tires (actual age, not exterior appearance), roof A/C, refrigerator, roof condition (no leaks), walls/floors for water damage (from old leaks), and generator.
