This is just an alternative to think about.
I'm inclined to look more at motor vehicles rather than trailers, for "empty box" camping. We did a lot of off the ground camping in the 50s and 60s sleeping in the back of station wagons based on the era's full-sized sedans. While today's SUVs are not so roomy as those wagons, we now have vans and minivans that quite a bit roomier.
For comparison on space inside, the standard Runaway at 46.5 W x 46 H x 94.5 L is a few inches less than what you would have in a Grand Caravan with both rows of rear seats folded into the floor, or any older "long" minivan with those two rows removed/folded. Floor to ceiling height will vary more on minivans across brands, but most try to match the 4 x 8 foot floor space of the Grand Caravan.
Another alternative might be a full-sized van. Mine is an ex-rental 12 passenger van, and I have 65" width wall to wall (50" at floor between wheel wells), 55" floor to ceiling, and 112" length behind the cab, 81" behind first row of passenger seats, 47" behind the second row. I took the third row out to make room for a conversion van convertible bed. A cargo van, without interior panels and insulation, would have another inch and a half of width, another two inches of height in most of the interior. An extended van would be 22-24 inches longer.
For price and weight, you should probably compare the Runaway to other 4x8 enclosed utility trailers available in the same area (for example, they cost about $1200 here). This will help to understand the added cost of the flooring, wall finishing, and windows.
As a towing problem, you need to find out the capacity of the Runaway, and figure out how much gear it will be carrying for camping. Weights being shown for the Runaway are empty weights, and to use it as a camping trailer, it will not be empty.