If you want to become a mystery shopper I think it is really important to check out this site first: Mystery Shoppers Manual. They give you all the information you (really) need and have a lot of tips to avoid scams. You can buy the mystery shoppers manual there which you can see below.
Never forget to get the right and needed information before you jump into this adventure. I hope you will like the tips our sites and other referred sites give you. Good luck!