The site you would use to market your part-time contracting could later be re-used as a sort of shop for related products, so you turn it into passive income and cash in on your marketing efforts twice.
My primary interest is not in a web startup though - my true love is Aerospace; I'm refining my math and other skills/knowledge so that I can minimize the amount of time I might have to spend doing pre-requisites and get the heart of an engineering degree.
I'm still on the fence about school, but I would love to pursue aerospace engineering.