It all depends on the agent.
They can charge anywhere from one month - 15% of the total year.
It is usually negotiated before the lease signing.
If you have any further questions, fell free to call me
edna mashaal 516-840-8888
Generally all commissions are negotiable, there are no set standards--the tenant pays commission, unless the landlord agreed otherwise before listing the property--your agent can best answer your question as it applies to specific properties.