Doing gunsmith type work covers a broad spectrum of tasks. Barreling is one and is pretty close toleranced work. I would suggest first taking a "continuing education" (after school) machine shop course. This will get you familiar with machine tools, micrometers, and gages. Foremost it should teach you to have a " light feel " and not be heavy handed when fitting sights, chambering and headspacing barrels, fitting a recoil pad, or any close toleranced job.
It should teach you about tolerances and just how big one thousanth (.001") is. Few realize that one sheet of standard loose leaf paper is about .003" ( 3 thousanths ) thick. Typical headspace tolerance is about .006". I would further suggest you read, read, read as much as possible. I am a toolmaker, retired from a gov't arsenal and can tell you there are many ways to do a particular task, some better than others.
Gun work requires patience and it should not be rushed, it is very rewarding when watching a customers eyes light up when he views your handy work. I have done hot salt bluing and found it to be very rewarding but also labor intensive. While I still have all the tanks and equipment I no longer do it as it was very time consuming. I was very picky about it and occassionaly had to start over on a gun because " I " was not satisified with what came out of the tanks. Perhaps I didn't charge enough?
Just don't give up your day job! This should start out as a hobby and progress from there. Chances are you'll make more money doing carpentry work than doing gun work. With our present anti-gun gov't. and depressed economy I could not suggest to "go for it". Pay attention, learn alot, and take it from there.