In Miami, the precedent has been set. All of the MLS listings have either one half month to each broker, so 50% of one month. OR, some offer 10% of the total yearly reantal amount. Either is acceptable, especially since we do many short term rentals here, the 10% of the term is often used.
I never see anything on the MLS less than this, as we are a heavy rental market and many of us must do many rentals to make our living and the owners are mostly absentee and need the service.
South Florida Brokers