Speaking from no actual experience, I can't imagine being a full time gunsmith is going to provide you with a steady income.

Not a bad thing to learn as a hobby or to make a little supplemental income.

The AGI videos are decent but I doubt you'd learn everything you really need to know. I have a couple of them somewhere on VHS. They were entertaining to watch and gave some good details of disassembly and reassembly but it's the trouble shooting and the machine work that really set the good gunsmiths apart in my opinion. A trained chimp can pretty much disassemble and reassemble something.