Yes, absolutely. Tenantancy is usually established after around 30 days of continued occupancy and once they are tenants, even if they aren't paying rent, you can't legally kick them out without going through the proper legal channels.

There's even been cases of people posing as fake real estate agents to "rent" apartments. If your dealing with a real estate agent then ask for their ID like you would a landlord, and the license number, and look up their real estate license online.