But realize that there IS a legitimate business of mystery shopping--if there weren't, we wouldn't be here chatting with each other. It won't make you rich, it is not always easy, you love it or you hate it, but there is a legitimate business.
Go to the New Mystery Shopper section of this forum and the top 4 posts are about how it works (Nuts and Bolts) and the other 3 are about extra helps and hints.