James,
I built two styles of tables myself. I bought folding legs (Home Depot,I believe) and mounted them on a piece of 3/4" plywood. (It's 30"W x 42"L) It's handled up to 200 lbs. On the top, used a rubber/vinyl matting I bought from a restaurant supply. Total cost under $75.

I also made an 18"-24" table again with 3/4" plywood mounted on a 2"x4" frame. The corners are framed so I can slip either 18" or 24" legs inside that are also 2x4's. For added safety, I drilled a 1/2" hole through the frame and the leg so I could slip a bolt through both and secure with a washer and nut. I use this at my studio mostly. (I'm at home. Sorry no pictures.) I am not "carpentry inclined" and I pulled this off.

Doug