Question about realtor fee's to rent out commercial property

[Dillon McGough]

Pardon my ignorance as I have zero experience with commercial properties.

I'd like to know the typical fee's paid to realtors for finding commercial tenants.  

I have a realtor friend that is negotiating a contract with a commercial building owner to lease out empty space in his building.  What does compensation typically look like for a realtor that advertises and brings in a tenant?  I'd like to know typical fee's if that realtor brings in a tenant that is not represented by another realtor along with the typical compensation if the deal has a listing realtor and a realtor that brings in the tenant?  Hopefully this makes sense