All startup advices, left and right, in unison say: it's way better to develop your product on somebody else's dime :) . Don't hurry to leave your work until yo

All startup advices, left and right, in unison say: it's way better to develop your product on somebody else's dime :) . Don't hurry to leave your work until your own business starts to fly. Go figure... What are the practical ways to benefit from side projects? It's hard enough to work on two works at the same time, would be sad if the results would be lost.