When you don't have an agreement with the landlord to pay your commission, then you simply must have one with the prospective tenants.
I don't normally work with rental clients, I prefer sales situations, but when I do, I require prospective tenants to sign a form that my office makes available for this purpose. The form basically says that if the tenants sign a lease for any apartment in the building(s) that I will be showing them--note, not only the apartments I am showing them, but any in the building--then they owe me a commission. Importantly, they must sign before I will show them any apartments at all. I have sent this by fax and received it signed before even meeting the clients.
No one has to use a broker to find an apartment, but if they want this kind of personalized service, they do need to pay for it.
As any experienced agent will tell you, you don't work with someone who has not signed a agency agreement and commitment to work with you, you don't put someone in your car and spend your time, energy, and gas till they have been prequalified by a lender you trust.
Speak with some experienced agents and have them give you their loyalty speech. Everyone who has survived in real estate has a dialogue that explains how they work, how they are compensated, and why if in exchange for their commitment to accomplish the their client's objectives, the client needs to be committed to be loyal and honest with them. Practice the speech, use it every time. While unlikely, these tenants may not have known the value of having you negotiate the lease, and the requirement you do so in order to be paid, perhaps they even think they made your job easier by going to the landlord directly.
You experience happens to every agent, hopefully it is not a reoccurring event and you learn from this experience.
RE/MAX Greater Atlanta
CRS, CRB, ABR, MSRE, CDPE, e-PRO, ESQ
Certified Residential Specialist
Certified Real Estate Broker
Accredited Buyers Agent
MS Real Estate and Urban Affairs
Certified Distressed Property Expert
Certified Internet Professional
2050 Roswell Road
Marietta GA 30062