Tvov has a good point, maybe you could do both. I built a home-brew camper and toy hauler from a cargo trailer. You could incorporate the dry bath, fridge, and A/C, leave the back for gear/kitchen/supplies, and still have the truck bed free for deliveries. All this at a cost that doesn't "double" your camper investment. Lots of the truck camper folks use the cargo trailer for gear or extended trips, (which I'm sure you've already considered).
Here's my basic cargo camper: (Warning, if you get too far off into that forum, you might never come back ha ha!)
Cargo Trailer Conversion
