Hi Richard!
Welcome to the forum!
Grab a coffee or some other beverage and pull up to the forum for a good read. If you start in the section titled New Members Section there is plenty of great advice on how to get a start in this business. You could also have a look at the "Official list of Mystery Shopping Companies." The link is at the bottom of the page. Another resource is company reviews in the Mystery Shopper Magazine, also linked at the bottom of the page. There are perhaps 80 or so companies reviewed there.
Have fun!
Happily shopping Rhode Island and nearby Massachusetts and Connecticut