After emigrating from Nigeria to the US to attend college, Tope Awotona worked as a door-to-door salesman and eventually set out to become a tech entrepreneur. He launched a series of e-commerce businesses that quickly fizzled when he realized he had no passion for them. But then he landed on an idea he was truly excited about: designing software that would minimize the hassle and headache of scheduling meetings. In 2013, he cashed in his 401k and went into debt to build Calendly, a scheduling service expected to make about $60 million this year.