Post this on the TRVN forum, you will reach many more Tiffin owners there. And shop the TRVN classifieds for a lot of good FSBO Tiffins.
This is the best resource you will find on any used coach, bar none, and is specific for a 2010 43QGP! Expect to spend a couple of evenings reading it all. Ted has made a lot of corrections, as well as a lot of improvements to this same model.
Crusingator's Files
It's a popular and highly desirable model that won't stay on the lot for very long, and therefore won't be sold at a low price. Don't take the sucker's bait from the dealer, as he merely came down from an astronomical asking price to something more realistic. Expect to need six new batteries real soon($1000). New tires in probably the next two years($5000). You could certainly negotiate both of these items into the purchase price, I would. And don't accept second quality on tires or batteries. Likely it will need the 'Big 3', but only Red Bay can check and tell you for sure. With the VIN you can call Tiffin to see if any/all have already been done. They can be done for free in Red Bay the first 6 years, so there is still time. However, expect to spend a month in Red Bay getting any/all of the work done.
Is it a 425hp(EPA07, no DEF) or a 450hp(EPA10, DEF)? The changeover was made around Feb 2010. Either is fine, the 450 probably gets +0.5mpg, but the cost of DEF probably balances out with the 425.
Which chassis? Spartan or Powerglide? Build date? The Powerglide has a couple of issues: An overweight front axle may be an issue. A number of 2010 Powerglide Busses were placarded(left of driver seat) at 50,900lbs with a 15,600lbs front axle, when actually built with a 14,600lbs front axle. Proportioning valves can be changed to lighten the front axle a bit. I would definitely weigh it at a CAT scale(3 axles) before I bought it. Not a deal-breaker, but an indicator of how much you will need to hassle with upgrading.
The exhaust flex pipe had a tendency to break. I've heard several revisions to improve the pipe. Tiffin will pay for pipe, you pay for labor.
It's a big coach to start with, if it suits your needs you will love it. Maneuverability in tight campgrounds is a challenge. Don't expect to visit many state/national parks, as most of their sites are too small for a 43' tag. Where will you store it? It has a long wheelbase and takes a lot of space to turn it around.
Have fun, it's a great coach.