I would suggest working your way up. Start with practice. Decide whether you want to form/join a band, or go it solo. Decide what sort of music you want to play. Cover bands (while they can earn a decent amount of $$$) rarely make a mint, and don't usually do it forever. Are you up to writing your own material? Audition...a lot. Work it like a part time privately owned business. Very few people started their own business earning major bucks right off the bat. Usually, it takes time to get to a point where a "self employed" situation will earn enough to be your sole form of income (if it ever happens), regardless of the kind of business.

I hate to sound like a downer, but it's a really difficult proposition to make a career of music. Not impossible, but difficult. I personally only know a few that have managed it in the Folk field, and of those, many have other methods of earning income (voice/guitar/whatever lessons, etc.).

I myself receive a tidy sum of extra cash from performing. It is a goodly chunk of change per year, and I am more than grateful for it, as it pays for things like Christmas and summer daycare for my kid. However, I wouldn't want to have to live on it, especially when several venues (some that you may have been working years) say "We're changing things out this year. We'll contact you when we'd like to have you back".