With some research, you might decide you don't want to make black powder. It really depends on what the final product has to look like. If you want lift charges for fireworks, surplus military black powder in large grain sizes, slow burning, is sometimes available for $2. a pound in certain lot sizes. You must have an FEL, which starts with a BATF-approved magazine, to buy it, and you have to pick it up in a legally-placarded vehicle. This grade of black powder is so slow it does not work well for cannon blank charges, and would be useless for cannon propellant.
As I'm sure you know, the harder part of black powder production is getting the proper grain size for your particular use. Anytime I've gotten the urge to make it, I began looking into it and always decided that buying the finished name-brand product was the way to go. I think I'd rather flip burgers at Mickie D's to make extra money to buy powder, rather than spend the same amount of time trying to make high-quality powder of the proper grain size.
I'd be interested to know what your make-buy dollar decision point is, is it $5. a pound, for example? I've heard that one importer sets up a stand at Friendship, IN and sells imported powder for $5. a pound, but i have no idea what the grain size or quality of it is.