Don't worry about something having a solid rear axle. Vehicles with solid rear axles were driving in snow for many decades before independent rear suspsensions were ever put in trucks, vans or anything else that can carry a camper/motorhome body.
Since you don't want dual rear wheels, that rules out practically all class C motorhomes. You'll be looking at van body B/B+ only.
If you want 4wd, look for a Quigley or Quad Van 4x4 converted E250/350 and then build the interior how you want it. Many of these are used as expedition, river rafting, or off road touring vans for carrying passengers on outings.