I think you might be happy with one of the RVs on the "Sprinter" chassis. It's almost a new category...larger than the normal "B" van, but small for the typical "C". One of the nice things, is the diesel engine, and the excellent fuel mileage that is reported.
Or you may want the to get one of the smaller "C" units that Winnebago or other well known brands produce. I think you will probably find them to actually be a bit less expensive than the Sprinters, and they will provide you with additional space, which becomes more important the longer you plan to spend in the RV.
The heavier chassis of the "C", will allow for a slide or two, as well as allow you to tow a Toad if you desire.
Best suggestion that I've heard of, over the years......is to go to an RV Show, and try them out for size.....lay on the beds, make believe you're cooking in the galley, sit on the toilet, stand in the shower......see just how well you fit.:)
THEN, you can make a more educated decision.
Good Luck