They have done stings in Seattle, where they call and ask landlords questions- do you accept Section 8? The landlord says no, and now the landlord faces a fine. What a smart landlord should do is make a website for their rental with pictures, etc. The person interested in the rental fills out the application, and mails it to the landlord. You can tell if the person is illiterate by a hand filled out application rather than a computer application with spell check. At that point, no discussion has been made. Everything is via the mail or computer. The landlord is then free to background check a person, determine their credit rating a job history. You can probably weed out the section 8 types, because they are either not working or have a low wage job. After that, then set up a face to face interview.
It would be very difficult to prove discrimination when the landlord does not make incriminating statements, and you cannot find out who applied for the rental.
You’re not taking disparate impact into account.