Let's say that a guy founded a new business he owns, and became CEO of his small company. Can a rich Entrepreneur offer that guy a job?
Yes. I can by all means start my own company and name myself CEO. If Bill Gates wanted to hire me, I'll take the offer and still be CEO of my own company. Now, whether or not my company makes money and survives is another question.
This is the basis of self-employed individuals who contract out their services.