Mystery shopping is getting paid to shop! You act as an independent contractor and secretly evaluate a company, reporting back to the mystery shopping company whose client is the company you reviewed. Mystery shopping companies should always be free to sign up for and be a member of. They pay you! Some companies pay a reimbursement for your costs (i.e. dinner, product, service) and others pay a fee and some combine the two. You can find many mystery shopping companies here who are registered with the Mystery Shopping Providers Association.
I am going to highlight the companies I am registered with in the coming weeks but you can email me if you want more information. Each company is different and has a different shop assignment system but the basic premise is you sign up to complete the "shop" you want, do what the guidelines tell you then scan your receipt and enter your report online. Some companies oay very quickly through paypal and others take longer.
My favorite mystery shopping company is A Closer Look so I will highlight it first. I have done many shops with A Closer Look. Most of the shops I have done were fine dining ($150 reimbursement) or casual dining, among others. A Closer Look just finished posting March's assignments so now is a great time to sign up!