Sidetrepreneur 

Someone who takes the initiative to start a business off the side of their desk, in addition to having a day job. A person who is an entrepreneur, investing time and or money to build a business on top of doing their existing job.

So very many people are still working their regular gigs but are spending all their nights and weekends developing an app or service, or building an entertainment franchise, or otherwise aiming to be the next Instagram, the next billion dollar baby.

"He's a real sidetrepreneur: he comes home from work every night and spends the next 6 hours working on this business he has started that will revolutionize the way movies are made."

Sidetrepreneur by NightsAndWeekends September 20, 2012