Find a rig, get in, close it up and just sit there for a hour or so. Check the furniture, shower, toilet for useability. See if you can get past each other in the walkway and see how long it takes to go stir crazy. After that hour remember that there will be days that the weather keeps you cooped up.
Look past the shiny things that will keep you from looking at the things that really matter. A granite counter top doesn't make up for a weak frame or foam core floors.
Think about how you intend to use the camper. when dry camping a larger set of tanks or more room for batteries will mean more than all the shiny do dads combined.
Haven't been camping or not sure of how you want to do it? RENT! The majority of rigs in the storage lot we use never move. I've talked to a few of the owners and well it sounded fun and they did it in the beginning.....It's a lot of money to spend and a big box to store and maintain if you are not sure.