It really all depends on the arrangement the landlord had with the realtor or rental agent -- whoever it was who helped you find your place.
For example, when I rented out my duplex, I paid the property management agent the fee for bringing my delightful tenants.
Whereas some landlords may not agree to pay that fee at which time the arrangement may be for the tenant to pay for the effort exerted in finding the tenant a suitable property -- the fee is one time, and it could be 1/3 of the monthly rent.
Before looking at rentals -- most of them would indicate what the arrangement is. For example "Fee paid" means the landlord is paying for it.