I have PPI punch list with about 120 points that applies to automobile.
You probably can make 200 points list when it comes to checking house part of motorhome.
When I would definitely check the engine for blowby, leaks and performance, very often you have to go with your guts on lot of stuff that you are simply not able to check.
I remember Country Coach was giving new buyers 2 days at their RV park to walk via coach with factory technician.
Who is taking more than 2 hr checking used motorhome?
If you have family/friends familiar with RV, you can take them with you and when one person will test plumbing, the other electrical and the most knowledgeable the engine and rest of drivetrain.