I am thinking of doing a sticky on this.
First, you can't be a half-assed gunsmith. Make up your mind whether you are going to be a competent smith and business man or a tinkerer who will louse up jobs, make people mad at you, and get your socks sued off.
First, everyone talks about an FFL. That is the very least of what you need, and the easiest to acquire.
If you decide to be a real gunsmith, you will need a training course. No, a video course is NOT enough, and tinkering a bit with your own guns is NOT enough. Then take a small business course. Gunsmithing is not about stoning a sear, it is about running a business and using your skills to make money.
Then raise some capital, because it will cost over 100 grand, probably closer to 200, to buy the equipment you will need to equip a shop and do the work right. That includes a good hollow headstock lathe, milling machine, top quality drill press, several post grinders, etc. Then add a bunch of headspace gauge sets at almost $200 each, welding equipment (electric, MIG, and gas) and a sight drill jig. You need complete US and metric drill sets (high quality, not hardware store junk), plus taps and dies. A heat treating furnace will run at least $600, a good large one is $1800. A bluing setup is expensive and even a Parkerizing setup that will handle a rifle is not cheap.
Now, think about those files and stones and screwdrivers some people seem to think are all that is needed to be a gunsmith.
You need insurance (may be hard to get), and someone to run the business end unless you are a qualified bookkeeper who likes 19 hour days. By that I mean a good bookkeeper, an accountant, and if you are open to the public, someone to run the counter. You can't BS with customers all day and get any work done. Believe me. And find a lawyer you can put on retainer if you get in trouble or some guy blows his own toe off and decides to blame it on the gun you fixed because everybody know gunsmiths are rich.
Then you need a place of business, properly zoned and licensed (no, not the FFL, the state and local business licenses, tax collection certificate, etc., etc.). You need security in the form of steel bars and an alarm system to protect your customers' guns, even if you don't buy or sell guns.
Even if it is legal to work out of your home, don't. If you do, expect to be waked up at all hours with guys demanding you fix their guns before the season opens in two hours. And remember, if you want to survive in business, YOU don't go hunting. YOU fix the other guy's gun so HE can go hunting.
Still interested? Still think you can hack it as a professional? Still think you can run a business you will enjoy and make money at it?
If you answer yes, good. We need more gunsmiths. There is a real need and a real demand for good gunsmiths. Welcome.
Jim