I built my own sheetmetal bending brake. I used some scrap angle steel pieces which I welded with my arc welder.
Scrap sheet metal is easy for me to find, from PC cases and discarded appliances. But to be useful, you need to be able to bend a nice clean straight line.
The base and bending lip were easy to make. I had a little more trouble deciding how to make the press clamp. My short-term solution just bolts straight down from the top.
My first project was a small set of drawers.