I bought a tiny, tandem axle, two stall N/S horse trailer for $225 a few years ago with no floor. Horse urine dissolved it decades ago. This was the final option (#3) for a bear-resistant trash trailer for our compound. I replaced the floor with two glued/screwed layers of exterior grade 5/8" plywood and primered and painted the rig brown. I also plated over all windows and open areas to further resist bears. It has worked well. I wanted to leave it rusty white and apply 12" letters that called a spade a spade, namely WHITE TRASH, but Jeanie did not cotton to that idea.
Here's what you need to know: This tiny old box made for Shetlands weighs 2500 pounds! Not quite bullet proof but made to resist horses trying to kick down the door. I've used my Cummins and my XJ to haul it to the dump. The XJ is way out of its league trying to pull this even with a Class III hitch. The every-six-weeks dump load is rarely over 250 pounds, luckily, so that part does not make much difference.
Contrast this with my 14 foot, wood plank deck, 7K GVW, steel framed, two axle car trailer on which I tow my CJ8 around. It weighs a measly 1100 pounds, dry. The moral to the story is, I think a horse trailer is too over-built and too heavy to be a good start for a make-over base camp trailer, unless you get it for free. If you do get it and fix it up, you will need a heavy duty tow vehicle to move it. IMHO.
jefe