This story is part of CNBC Make It's Six-Figure Side Hustle series, where people with lucrative side hustles break down the routines and habits they've used to make money on top of their full-time ...

Mike O'Dell didn't feel fulfilled spending his entire workweek as a nurse anesthetist. He was a creative and a risk-taker — not exactly qualities that mesh well with anesthesiology, he said on last ...