After some thought, it seems "basic" might be defined.
What's the intended purpose? Week end camper/toy hauler/ long term camping or do you intend to live out of or in it? Why do you want a trailer?
How many people/kids/dog/cats/critters would occupy the trailer?
Do you just want a safer and dryer place for a bed roll? Do you require a bed? What kind?
Any inside activities? Sitting/pooper shoot'n/bathing/cooking/eating/playing games/watching computer-TV/singing or dancing/just gett'n drunk?
I'd think what you intend on doing, (with all of the above considerations and most likely more) will drive your needs to prepare your "basic" trailer.
Seems a basic trailer to live in by yourself at Quartzsite would be a lot different than a basic trailer for 3+ your dog for a venture through Alaska to the Arctic Circle in March.
I would consider my trailer to be a bare bones "conversion" (actually, alternative use), but with some convivences.
When I bought my 6x14 x 6.25 V Nose, I had not intensions of making a camper out of it, it was to haul my 1800 VTX Trike and tour the country staying at military installations, motels and perhaps a few cabins. I bought it used just before Covid hit us. A 2018 Razorback, I got a very good deal, no dents, scratches, nice wheels, painted interior with hanging/securing hardware inside.
I have enough camping equipment, kitchen/porta pottie/cots/solar generator and toys to through in the trailer and take off right now, nothing needed to go to the lake. But, I plan on making it more living friendly.