Re: Frame Building questions
I can attest to the fact that welding thin metal like bike frames is not easy if you've never welded before. However, with some experience, you can do it right with a regular $100 welder from harbor freight. I've seen some welds come from good welders on the HF flux core unit that put some mig welds to shame. It's all in the preparation of the metal and your skill/patience level.
I would not start with a motor bike frame first. You could weld up a regular pedal bike and give that a go if you wanted to try it. For the cost of a welder, a pipe bender, and all the materials... I'd seriously just buy a frame. I can weld fairly well (with my own quality Lincoln welder), but I'm not about to spend more money on a pipe bender to make a frame.
Just my opinion