Is it permissible for the agent to take a "finder's fee" commission from buyers of real estate inherited from his father?

Taking a commission from buyers is not permissible unless authorized by the heirs who appointed you to sell the properties. This is because such a commission is considered an increase in the price and rightfully belongs to the client, not the agent. Furthermore, taking it may lead to favoritism towards the buyer, which contradicts the trust placed in you.