Now that's an idea worth stealing If you enjoy math, then this could be fun too - since most of the problems would be pretty basic stuff from lazy kids.
There are many job oppurtunity waiting for you.. like online tutor, make an mathematical article, make your assignment and sell you your classmate! lolz
this one is good idea. also do what W3bmaster suggest is a good idea too.(if you knwo how to make a blog or a site or can pay small money for hiring people do it for you)
I would recommend that you start a forum where you and other members could collaborate to answer questions. This would gain far greater popularity as it is free, in addition to eliminating any stress associated with not being able to answer certain questions that you've already received payment to be answered.