Howdy partna!

Alot of us are in the same sort of situation as you in terms of space. I used to have a garage but when I got divorced, well... Anyway... I keep a corner of the room reserved for fotography or painting or whatever. I tend to build on the ground simply cuz it's easier to cut foamboard on my knees than raised up. (I put a piece of wood underneath and I often paint on the floor too.

All my sets are modular. Therefore, i have a bunch of wood bases w/ L-brackets screwed in. I set my foamboard walls against those. They break down easily and i can use them in the future often by just repainting them.

Check out my dios to see what you can do fairly easily with a 48"x40" space. (two cheap tables from the store placed next to eachother, storage space underneath...)