I think it's rather rare to make a really good living from music or any other performing art, for that matter. I just read a review of a play in the paper that mentioned the fine performance of one of the actors--it was the carpenter who built our back porch. The job took a little longer because he had to take off in the middle of the day for a voice-over audition.
I have had the great good fortune to get to know a number of very fine musicians, and with the exception of a couple who are retired, they all have day jobs. Only one of them has a day job that has anything to do with music, and he also has to give tours and lock the restrooms.