let's be clear about something here before we begin:
Everybody is an expert (or "expert enough") in at least one body of knowledge. It doesn't matter what it is.
Maybe you know how to sing a little bit better than everybody else, maybe you know your way around the basketball court, maybe you have discovered a way of running a little bit faster, or maybe you know how to make money with Twitter or Facebook.
Regardless of who you're dealing with, everybody has at least one area of expertise.
Since this is the case, did you know that people might actually pay for your expertise?