It's mandatory to have a single unit? Reason I ask is there seem to be a lot of concession type trailers around. Why not convert the truck to whatever type of living quarters you want and get a trailer for the sales? That way if you ever want to sell you'd have much more saleable items.
'03 Freightliner FL112, 295" wheel base, with '03 United Specialties 26' living quarters, single screw, Cat C12 430 h/p 1650 torque, Eaton 10speed , 3.42 rear axle ratio