If I could guarantee that I'd have enough business to make more than what my "regular" job pays, then I'd do it in a heartbeat.
Though, my GF just got a job offer at a new company, that if all goes as planned, would lead to a 6 figure job for her in a few years. At that time, if I'm still in the same salary range, we should be able to afford for me to start my own shop. Until that time, if it ain't broke. . .