I know someone who ran a mystery shopper business. She "paid" the shoppers in merchandise they bought on the job. The shopper would have a list of things to ask about/try to find in the store. They would look to see if the employees were wearing their name tags, was the store clean, whatever the store owners wanted to know about.
Mostly they purchased up to $25.00 worth of merchandise and the shop lasted about 30-45mins. I know this is done for restaurants, too, but I don't know anything about that.
This person I knew hired her friends and neighbors.
Hope this helps.