From the NFL to WordPress themes
Drew Strojny, former NFL player for the Eagles, Giants and Rams, had been moonlighting as a designer and open-source WordPress theme developer for years. The theme business, which is supported via support-membership-subscriptions (great business plan) is really taking off. So much so that he and his wife are doing that full time via The Theme Foundry.
Recently Drew wrote up the backstory to how this all happened and it is a fantastic read.