I would like to run an ad for computer repair to make extra money. Is it legal without a liscense?

I’m fifteen years old and I work in a kitchen at a club, obviously since school is back in session my hours have been cut, I really need the money, and I’m very good with computers (both hardware and software). I would like to run an ad for computer repair to make some extra cash. [...] http://bit.ly/nW9QR1