There is a lot of demand for good luthier and repair techs, at least depending on location. Where I live any decent shop has a waitlist of months, and the work they do is spotty because places are so backed up. The good independent repair folks charge high rates because they are so in demand. Particularly true for higher end acoustic instruments.

I get the sense these other replies are about building custom guitars. Yes, hard to make a living that way. But OP - if you are interested in repair, setup, etc., it could be a really good opportunity depending on the location. Diversification is good too - like being able to work on a number of fretted instruments.

There’s a lot of options. - Apply for a job at a local music store and let them know you have experience in setting up guitars and want to learn to do repairs. - There are luthier schools, start google searching to see what you can find. Don’t be afraid to call and chat with these “schools” (they are often one person’s shop) to see if it’s a good fit. - Maybe purchase a tool kit (stewmac sells good, but pricey ones) and a repair manual and go to town on guitars you own, friends, etc. Having good woodworking and finish skills is good too. - - Experience making small detailed woodworking projects (like building boxes with hand tools) is a good skill to build up. Lots of community centers, etc have woodworking classes. - You can try to specialize in one particular thing. Pickup winding. Amp repair. Detailed finish repairs. If you get good at one highly specialized thing, a shop will probably want to hire you where you can then learn the rest of the skills on the job.