Is it permissible for the broker to receive payment from the car’s owner in return for selling it for him?
Question

A friend said to me: I want to buy a car in return for deferred payment; do you know anyone? I said: Yes. I went to the car’s owner and told him: I have a customer for you, but I want a broker fee without my friend finding out. What is the ruling on what I did?.
Praise be to Allah.There is nothing wrong with working for a seller or a buyer; there is nothing wrong with stipulating a condition in that case."(Majmoo’ Fatawa Ibn Baz  19/31). 
See also the answer to question no. 45726, in which we explained that it is permissible to accept payment for brokerage, so long as the broker is trustworthy and honest. 
And Allah knows best.