This is interesting. It gives some insight into the possibility of turning some basic secret shopper skills into a consulting business. For some businesses, it makes more sense to get a snapshot from one person with experience rather than anonymous shoppers coming in on a monthly basis. I would imagine that is one way to set up a mystery shopping program as well.
In the show, she takes on clients who cannot afford her but there are plenty of stores and restaurants with a small number of locations that have money to invest.
I had someone actually ask me about doing something like this for a charity thrift store. Not for pay, of course.