We boondock in a 24 foot Class C motorhome that sleeps six - in two permanent queen size beds and one convertible full size bed.
Granted it only came with a 29 gallon grey water tank, a 38 gallon black water tank, and a 45 gallon fresh water capacity - but if push comes to shove we can carry more fresh water with us and we can dump grey water in the bushes the same as tent campers do. The black tank is pretty generous if you teach kids when and when not to flush and how long to flush (like we do with our grandkids). The two of us just completed 9 days of drycamping and filled about 1/4 of the black tank.
We have drycamped and boondocked camped in many spots with our 24 footer that I would not want to wrestle a TT or 5'er into. It's high ground clearance (oversize tires) and upswept rear over-hang helps too.