Welcome to the MOC!
As newbies to the world of RVs, there is a lot you probably don't know. And buying from a private party might get you more information than an used RV dealer, it may not get you all you need to know.
The best route if to take a RV literate friend with you to help. There are also RV inspectors you can hire to look at the RV before you purchase. Any help you can get is a benefit.
There are many Pre-Delivery Checklist (PDI) documents floating around. They try to list everything you should check to make sure devices and systems are operational *BEFORE* you sign a contract. Dealers try to get you to sign with a promise to fix it later. But later never seems to come in a timely manner. Hence "you fix it now before I sign.." is a huge motivator. As you appear to be buying from a private party, a warranty doesn't exist so there is even more reason to ensure things work before you buy.
Here is a link to a pretty comprehensive PDI list here on the MOC.
https://www.montanaowners.com/forums...?do=file&id=87