pcoplin,
Keep this in mind when shopping around. When it comes to roll-over protection in a class C, nearly every manufacture compromises that protection by cutting the cab roof for easier access between the two front seats and the house, as shown here.

Regarding 3rd and 4th person seating, most floor plans provide "Seat-Belt" seating in the dinette which does not meet NTSB standards for typical automobiles. The only affordable used motorhome I know of that has real seats for four adults is one of the popular Rialta floor plans. But that rig falls short when it comes to "practical" motor home features.
Our 2007 rig
HERE has a true 3rd person seat but only with a lap belt. The seat swivels forward to rearward. Unfortunately that person's outside view during travel, is limited to the front cab windows. Fortunately there is a good view of the TV.
Our brand of motor home is offered with a Quigley 4x4
HERE, but there are very few used ones out there to find.
My personal thoughts about a 4x4 motor home is that I really would not want to subject the house to those extremes. There are a few exceptions like the Earth Roamer, Big Foot, and Tiger to mention a few. But a conventionally constructed motor home has enough challenges keeping together on regular roads, let alone on roads that will twist the frame which then will breach seam work. Routine treking through sand and mud would be an exception to the 4x4 world.
I just did a quick search on "Phoenix Cruiser 4x4" and found
THIS 2009 2350 4X4 for sale.