And for those of you who don't want to do it yourself, I might be persuaded to sell finished instruments or parts. Mandrels are used to support tubing during forming, resizing, soldering, etc. Metal tubing mandrels Very nice hard mirrored finish mandrels can be obtained by taking apart an old printer, especially a daisy wheel one. Hammers Rubber Mallet is useful for banging on things you don't want to mar. Great for cutting brace material and perhaps tubing.
Equipment is much more expensive.
Acetylene - used by repair shops and welders as it has the highest heat of common gases, but cylinder rental is expensive and there is a theoretical risk of explosive decomposition without the presence of oxygen. Solders - low temperature joining alloys. Must be without flux core, and ideally in smaller diameter than used for plumbing. Most require appropriate flux, which is nasty, toxic stuff. Might work well for assembly if available in small diameter.