For those that are unsure basically mystery shoppers are people that go into shops, restaurants, hotels etc and feedback on the service.
Recently I thought I might like to give this a try and so set about researching the various companies that sign up mystery shoppers. At this point I must tell you to beware, there are companies out there who ask you to pay to sign up with them and I really can't see the point in this as there are many out there with excellent reviews that charge you nothing whatsoever (after all that would defeat the point for me!).
I read a lot of good things about a company called Grass Roots https://www.grassrootsmysteryshopping.com and so have recently signed up to them.
I will let you know how I go as time goes on but so far I have found them easy to use and I like the set up of their site. You can add up to 5 locations that you are willing to mystery shop in (e.g. home, work) and also specify the times that you would be available at each address. Assignments are then emailed to you whenever they become available in these areas and you can choose whether to accept or decline once you have read the brief.