The trailer has 3500# axles and weighs 500#. I plan on using light but strong materials, at least in my price range (less than $1,000 total). It will just be for me to use while working; place to stash clothes, cook a small meal and catch some sleep. I also have to do this in stages, as I can't afford to do it all at once. A couple of pieces of plywood one payday, etc..
I believe my ramp is 48", which will make it a useable 60sqft. I plan on following a build I saw on the net, similar to a fold down camp trailer. The 3 sides will be fixed, but the roof will be fold down and the ramp extensions (and that roof section) will be removable and stored inside the trailer during transit. The bed platform will be hinged for more space when not being used and it will have the bare essentials (vying for all electric; I can get small 110V appliances that will fit the need, and I always see them at Habitat and junk stores for cheap). Really want to avoid the hassle/expense of plumbing gas.
Essentially, it's a short term solution. Like the Burb, which I bought specifically because it's a 2500 and needed a motor/trans refresh (and had never done one) and the shed, I could have just bought something in better shape or ready made for more money (and saved a ton of headaches) but I'm also doing it because I want to prove I can use my hands for something other than turning wrenches.
If this works out my next build will be a 30' race trailer. I hate the thought of spending what dealers want for even a basic nothing rig these days, not counting their fees. For now I'm snowballing ideas.