I worked on top of my full time job doing web dev for Ad agencies, usually php, asp.net or CMS work. Billed at $80/hr, probably netting 40-60k per year on the side. I had always hoped it would lead me to a career as an independent, but that rate is not enough to make a living with a family. I eventually made it to being an independent, but I had to switch to doing enterprise consulting in a niche market at a much higher rate.