I wouldn't rent. You said you were going to "chuck it all in for a while", and if that "while" is more than a few weeks, it will be way cheaper to buy a used class A or C, take the trip and sell it when you're done.
For under $25k, you should be looking at 20 year old diesels and 15 year old gas models. Figure on spending at least 10% on fixing stuff the first year. Get someone who knows what they're looking at to inspect a prospect coach.
And I agree Dave - just the 2 of you, moving a lot, take a hard look at class Cs. It will cost less to run than an A.