Thinking about this more...
I assume you got the flip-up side idea from Amazing Spaces?
Be aware that that will involve a LOT of extra metal framing. Cutting the side removes all of the structural integrity of the truck box -- you will have to build a whole new framework for it, of a different, more complex design. If you saw the show, they did not go into detail but they have the whole RV down to the studs.
Plus, that moveable side weighs multi-hundred pounds, so you will not be lifting it on your own. You will need machinery.
It would probably be cheaper to buy some land and build a house ;).
