We just switched from a converted cargo hauler to a TC. We bought a used 8x20 Pace American Car Hauler and added: Kitchen with sink, small fridge, a lot of counter top, Microwave, and cabinets. Also carried a two-burner hotplate.
We added a full size bed along one side allowing enough room to park our 650cc Scooter on the other side. We ride two-up so only needed enough room for one "bike".
We also had an electric recirculating toilet in a "closet" type enclosure. We then added a closet with hanging space and a four-drawer cabinet in the bottom.
I cut-out an opening for a small window unit AC and we used an electric heater. It had two ceiling vents and one window.
Why did we swtich? Two main reasons: 1. We wanted our cats to be able to walk from the truck's cab into the RV area. 2. We did not like having to take out the scooter every night when on the road. Gas fumes can be dangerous if you sleep in a ToyHauler with the vehicle in it.
Best advantage of our home-built unit: Everything except the toilet could be replaced with items from Lowes or Home Depot.
Del