Other cherrypicked examples, Dave Grohl and Clapton famously had no formal training and just learned by listening to and emulating artists they liked. I suspect they make over 20k/year.
Dave Grohl knows his scales now. Yes, if you make a band and become successful you can call yourself a professional without music theory. If you go back to what I said though, I said as a degree.
gabereiser|2 years ago