Based on a Force 3700 WB this caravan easily sleeps 4 on board

Amenities :

• Convertible dinning come bed combining into a queen sized bed.
• Double drop cab over bed that sleeps 2 
• Pneumatic activating valve based washroom : with a basin, commode and shower with hot & cold water supply
• Kitchen : burner, sink, microwave, 12/24 VDC fridge

If you are dubious about getting one built, you can also rent this or similar model and get the gist of caravanning, experience your own Motorhome Adventures