Maybe I am missing sinhteomg here. The agent might be acting in one of two different capacities. As an agent there is the <> duty and they will take a fee for acting as agent. On the other hand, they act as a tenant in their own right and the terms of the tenancy agreement gives them the right to sublet. They are no longer an agent and therefore their best interests duty goes. This is not underhand if both parties know what is happening and enter into the relevant contract knowing what they are doing. So the question for the landlord is <<would I rather rent at a3650 to a reliable corporate entity, when I can be sure I will receive the full rent for the year on time and allow subletting (with potential commensurate issues like transient occupation)? OR Will I rent for the maximum monthly income but have the standard risks of non-payment and voids? Only the landlord can do the calculation based on their appetite for risks?