Welcome to the forum from Kansas City, MO.
Glad you're here.
It may be a good idea to get someone who is more familiar with campers locally to help you look it over. You'll want to make sure that everything works or you'll be inviting problems later. Here are some things to check:
Tires: How old and what kind of shape are they in.
Brakes: Are they functioning?
AC: Does it blow cold? Is the fan noisy?
Furnace: Does it blow hot? Is the fan noisy?
Water pump: Does is work?
Appliances: Do they work? Does the fridge cool on electric and LPG? Does the stove work? Microwave/oven: do they work if included?
Lights: Inside and out: Do they work?
There is a starter list, I'm sure others will chime in shortly.