What kind of tournaments can I host to make a profit?

I want to begin hosting tournaments as a summer job and i'm considering sports such as basketball, tennis etc., board games like chess and checkers, card games like blackjack or poker, or video games like super smash bros or cod modern warfare 2. I want to know which are illegal for me to host without permission and which I can do without a problem. I know i'll probably need sponsors but I don't know where to begin looking for any.