I do shops for Starbucks and a regional grocery store chain. I found the shopping companies on
www.volition.com , a website that lists non-fee shopping sites. I wouldn't ever pay to get on a shopping list- those type of sites are usually scammers.
With the Starbucks shops, I get paid a certain $$ amt per shop, and am reimbursed for the beverage I buy. They tell me the date,and time to visit, and the exact drink I must order. When I return home, I log in and type a report on their website. I observe the store atmosphere, associates, and test drink temp and weight.
At the grocery store, I am required to make a $5 purchase (which is NOT reimbursed) and am paid a $$ amt per shop. There are several different types of shops to do- usually, I interact with associates and rate the service provided. I fill out an online form at home.
I enjoy it, and I average around $200/month. It's great- I schedule shops around DD's school hours, and I usually end up actually working about 15 hrs a month. The IRS lists mystery shoppers as independent contractors, so no tax $$ is taken out of payments (you will receive a statement from the company if you earn more than $600 in a year). You need to set some $$ aside for taxes, but the govt also will pay you mileage $$ that pretty much offsets the taxes owed.