Not a gunsmith, but starting a firearms-related business after finally reaching the frustration point with the construction industry here in FL...
That said, for a lot of years I had $1MM plus in revenues at a decent profit, and a B.S. in Business Admin- so I feel qualified to chime in and second the good advice James K gave you.
If you want it to be your livelihood, you have to earn a profit. And to earn a profit, you need an understanding of what your expenses are.
ALL your expenses... "What's General Liability and Product Liability insurance?"
If the school offers, take some general business/accounting classes. Trust me, you'll need them, to be successful...
That is, if you plan on going into business for yourself someday, that is...
Some guys, aren't interested in that, and that's fine (and often, the better route...). In that case, just learn your skills- and let the owner worry about whether he's charging enough!