These days the best way to get into the trade is to attend a top gunsmithing school like Colorado School of Trades or Trinidad Junior College.
Once you graduate, go to work for someone else for a few years. This will allow you time to really learn the trade and learn how to do quality work....fast.
It'll also give you time to get a reputation in the industry and build up a possible customer base.
Starting your own business is RISKY at all times.
Most gunsmiths fail, and most fail because they know nothing about how to run a business.
Remember, you will not be a gunsmith. You'll be a businessman who happens to run a gunsmithing business.
If you don't know accounting, tax work, filling out forms for the government, dealing with customers, and ordering parts and equipment, no matter how good you are at gun work, you'll fail.
This is why smart prospective gunsmiths take business classes along with the gunsmith training. Some schools offer business classes, so TAKE them.
Last, don't expect to make much money. The only people in the trade who make much money are people like Bill Wilson who own large shops and have a number of gunsmiths working for them.
Probably the smartest gunsmiths spend their career working for someone else.
There's an old joke: "How's a large pizza and a gunsmith alike? Neither can feed a family of four".