There's a link at the bottom of each page to legit companies. As far as the kinds of shops, those are going to vary because as contracts expire, some client companies will change the company thst does their shops. And I'm not sure what you mean by "employer". As a shopper, you would be an independent contractor, not an employee at all.
Peruse the verious threads on the forum; you'll find most of what you need in those pearls of wisdom.
"To be persuasive we must be believable; to be believable we must be credible; to be credible we must be truthful." Edward R. Murrow
Thou shalt not steal. I mean defensively. On offense, indeed thou shall steal and thou must.--Branch Rickey