The key right here is “potential” landlord. This is a rip-off.
Some folks submit pretend adverts for rental properties and inform all “prospective tenants” to join a free trial in order that they get an affiliate fee for every trial enroll.
If you have already appeared on the place then it is a completely different story, however my guess is that the place you are taking a look at more than likely shouldn’t be even out there.
Tldr; it is a rip-off.