In your described scenario, it looks like both Agents were keen on getting a Full-Fee and charging the Tenant for 1.5mo rent is a bit uncommon in MA, but certainly possible (in NY, a Tenant might be charged 10-15% of a yearâ€™s rent as the fee).
Bottom line, both sides (Landlord & Tenant) should have received clear disclosure from their respective Agents on how their Fee structure works, on how they expect to get paid (and from whom) to complete the transaction.
You can only clarify what you are required/requested to pay.
The tenant's agreement is a separate agreement that you are probably not a part of.
Unless there is a clause in your agreement that says you get to know what the tenant agreement says, and that you get to adjust your fee accordingly, then you have to decide if your personal agreement was useful and complete.
If you got a good tenant, if the fee was comfortable and correct, any other income to the broker should not affect you.
That may sound callous, but you and the real estate professional have an agreement that the tenant is not a party to either.
If you how the professional operates, don't use them anymore or modify your future agreement(s).
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Maria E. Cipollone