Not long ago I had an interesting discussion with my coworker about our jobs. As a sysadmin I often get requests from people that know me to help them configure their server, set them up a web page, mail account, etc., for a small fee. Or from some small company that does not have the expetrise to maintain their own server. But I gladly pass all such requests to the coworker, because I can's stand the feeling that any of those people would have the right to bother me at $random time of day because of some irrelevant problem, like spam getting through or somesuch. He offers them his price and then they deceide if they want him to fix their systems or not.
On the other hand, if someone ask me to teach him how to do all the system administration and is willing to learn, I'm more than glad to help. I don't even ask for a price, I just say if he feels like paying me, he can pay whatever he feels is the right price for the knowledge I gave him. But just the satisfaction of teaching someone is more than enough for me. I guess I got this after my father :)