For what it is worth, if you find the previous owner, then you might look for a forum for brand specific RV's and see if the owner was a member and had posted about his RV.
One of the forums I belong to is for a specific types of RV's and if you were looking to buy one it could educate you on common issues and solutions. If the previous owner was a member, you might be able to read where he had some serious problems that were either corrected, or might be a remaining issue for a new buyer.
Basically the internet is your friend. Use all of it to gather information about any major purchase.