I got a metal pipe from a chain link fence I was tearing down and used some scrap lumber for a frame. It isn't perfect, but I'm not that handy or picky.

Places that pre-fab houses/ trailers/ pallets often have a free bin where you can get shorter pieces of lumber. Maybe some equivalent for metal bars or pipes (welding shops? fencing companies? Plumbing or gas fitting? Places where site / building demo is happening).

Where I live it is illegal to take things from the landfill and they are quite well monitored.