i have built a startup on the side while working full time still. due to the fact that we are 3 partners, the money is not enough to quit my day job but it's getting there. we have grown from $0 to $200K in 2 and a half years while all 3 of us do this part time. i did all the development and sysadmin work and the other partners took care of the marketing and business side of things.