Take your time, took me a year to find my Sunrader. Found it one Saturday morning on Craigslist. Prices will vary depending on mileage and condition, just like a car...mine was priced fair for a 60K mile vehicle.....but they absolutely hold their value well if you keep it in good condition.
My main suggestion is once you narrow down to a few, take your time to check out everything. Try each plug, have the owner cool down the frig, turn on the heater, A/C roof unit. Pour some water down each drain, look for leaks, use a hose on the windows and roof.Feel for saggy, soft floors. A set of tires will cost you over $1K so make sure they're in good shape...make a checklist and follow it......good luck! They are great fun and this is a good site for support.