Lots of people list a property, take loads of applications, each with a nonrefundable application fee (often $100+), then close the listing and pretend it was leased out. They wait a bit and repeat the play. They can rake in thousands of dollars for literally making a posting on a website, and repeat this often. And it’s often desperate people victimized too: not only are these people renting so they’re already in a vulnerable situation, the people willing to pay high application fees typically are desperate to get a lease.
I’ve also seen places that make you pay an application fee, and as part of the screening process they run a credit check; if they aren’t satisfied with your credit score, they’ll deny you and of course keep the application fee. What’s more nefarious about this though is that they don’t give you a score cutoff; you don’t know if your score meets their criteria until after you’ve paid a nonrefundable fee.