I think TJ has hit on something that was key for me.
I worked full time (managing a folk music record label) for a number of years. I was fortunate that my full-time job was related to my music. Through my job I learned a lot about the business side of music, and I got to meet and establish relationships with a lot of people in my work role. I can't tell you how invaluable that was. I feel incredibly lucky to have had that opportunity.
Then, when I quit working full time, I managed to find some part-time work that was very flexible. I got a decent hourly rate for it, I could set my own hours, and it was work that I didn't have to take home with me. My employer knew that music was my first priority, and was able to allow me to take a few weeks off at a time if something came up.
Having that job is what allowed me to make the transition to full-time music. I had time, I had some income coming in, but I had to make up the rest through gigs, CD sales, etc. And gradually, my music income went up, until I was earning more money from music than from my part-time job. At that point, I took the leap and quit the job. And I've never looked back.
So I consider myself extremely lucky in the job department. If you can find a part-time job where your employer knows your situation and is willing to accommodate your music career, you are in an ideal position to test the waters and see where music might take you, without having the huge stress of having to earn ALL your income from music.