I assume you want to do this as a pocket change garage project. Anything more serious is going to put you in need of a lot of training, and if you want to make competitive goods it will take a lot of money to set up a decent shop, which every farm in America already has. So along the hobby lines-

>One idea is take a trip or find some books about Mennonite welders in rural Pennsylvania, those guys are the Cuban fender menders of America. If it can be done for a few hundred bucks, they can do it.

>Ask a custom gun shop who they have doing work for them and ask that person how he got into it and what he sells.

>This guy is an old friend from many years back who got fascinated with making custom tactical flashlights when white LEDs first came out in the late 90s. His first designs were very basic, and now he has some pretty sophisticated stuff. To this day has been evolving his designs out of a garage. The apparently sell, which is amazing considering how many Chinese flashlights there are at Walmart.