About the time the OP was asking this question, I was asking the same questions. So I bought a lathe, and been buying tooling, been playing around with it practicing turning, threading, boring on various projects. I've read hours and hours of online stuff, and several books on machining, and chambering rifles. So far if I had to guess I'm about $8,000 into it and am just now getting ready to order my first chamber reamer to try and cut a chamber in a barrel blank I bought. I dont think it takes 3 years to get comfortable for everybody like it did for me, but it's a matter of how much time you spend running the machine and trying new things, which for me sadly was not often enough.
It's not practical for me to take off a week and fly across the country for a gunsmithing course. And I have no community college opportunities nearby offering machinst or gunsmithing courses so I've decided to try the self taught method. I have no intention of becoming a gunsmith and working on other peoples rifles. I just like the thought of doing it all myself.
Of course when I first started lookin into it, I thought I could save some money by learning to do everything myself, but that notion got tossed out the window real quick. Shortgrass was right, it will take well over 20 barrels to break even, and that doesn't take into account the time I have invested into research and practice, and the time it will take me to actually perform the work, if a dollar amount is applied to time spent it's a terrible investment. DIY in regards to this topic, in my opinion, is a road you go down only because you want to be able to tell everybody "I did it all by myself", kind of a pride issue I guess.