I didn't see where anyone gave you a link for a PDI Here is one.
Doug's RV Checklist Page
Print out a couple copies. When you thin you have found the one you are going to buy, give that dealer a copy and tell this is what to expect when you do your PDI
Familiarize yourself with that PDI, take it with you when you go to pick it up, AND adhere to it. Plus don't pay them until you are satisfied that everything works. Make sure you understand how it works even if you have to go back thru it again.
If you have a video camera take it along and have somebody do the filming for you. Believe me, you aren't going to remember it all.
Good luck