Please don't be misled by NADA. Buying an RV is not comparable to buying a car or truck. NADA does not equal Blue Book value. Vehicle vs Rv are 2 different types of markets. With an RV, condition is everything. Wholly agree with others that you must have a qualified RV inspector check out all the major systems, and someone to look over engine. Have you asked for any maintenance records on the unit? You can/should inspect the interior fit and finish - look inside all cabinets, do doors close and stay closed, condition of bath and sinks, toilet, floor/carpet, do the blinds work easily, do windows open and close, pull on all the trim to see if it comes loose. Take your time and look at everything, not just a glance. Are the tires past their date codes and need replacing. It's a bunch of time and effort, but to better determine if the unit and asking (or your offer) price are in line, it needs to be done.
Then, even with that, you should have a stash of cash to pay for inevitable repairs or replacement of things. How much? Don't know, but $2000 to $3000 would be a good start. Their will be maintenance costs as well, so the amount could help cover those items as well.
Bottom line, if everything checks out - even if there are some items that need attention -- is if the unit is worth the cost to you. If so, go for it and be happy in your new travels.
Linda