I agree with cutting brush AND with Vixen! I believe that it is a good idea for a young person to fend for his/her own cutting brush or flipping hamburgers as long as they also have the full responsibility for their own rent, car, food, & other living expenses. It is amazing what a year or more of poverty can do to motivate a person to be serious about additional education (either formal higher education or the trades).
Also there really is no hurry. Spending a few years to 'find' oneself, is truly an investment in the future. After several false starts, I finally got my bachelor's degree at the (then) old age of 27. It took the Marine Corps to motivate me.
Vixen is correct about perhaps starting out in a local community college that will provide good down-to-earth counseling. I like her idea of 2 "real" courses along with a music course as a reward. Don't be misled though, music, as an academic discipline, is not easy! It ain't engineering, but it's also not "American Studies" or some other 'pud' course. The military is also a great growing-up motivator.
I'm with a large university in a non-teaching position, but I do work with a number of engineering students, mostly grad, some undergrad. Unfortunately, very few are Americans. Our local schools are just not preparing our youth for the academic rigors of engineering, science, and business administration.
Hopefully, your son is one of these highly talented people who can be successful either in or out of the music business without formal higher education.
For you Dad, you done your best to raise him - I'm sure he has inherited the good character that will lead him down the right (perhaps circuitous) path. My most sincere best wishes for him.