Pare your kit down to what you really, really need – and it’ll also make you a better builder I think. You can build a perfectly straight frame with no jigs, just a bench vice and a piece of string. Filing miters by hand is a perfect way to understand how the tubes go together. Stuff like that.
Don’t make road stuff. Roadies want a cheap frame with a bling paint job – unless you can do the paint job yourself, you’ll be giving most of the profits to someone else.
Practice, practice, practice. Don’t sell the first few frames you make, ride them yourself or give them to mates.
It’s a hard business to make money at – but it is also incredibly satisfying :-)