He works in a paint shop and directs customers to a painter in return for a percentage
Question

                I work in a paint shop and my salary is low, but people come to me and ask about a painter to paint for them. I have the numbers of some painters and I try to recommend them to the customers in return for a percentage that the painter gives to me. Is this percentage haraam?.
Praise be to Allah.
      There is nothing wrong with telling the customers about 
      painters in return for money that you take from the painter whenever a 
      customer comes to him through you, whether that payment is a set amount or 
      a percentage. This is what is called a broker’s or agent’s fee. It says in
      Fataawa al-Lajnah al-Daa’imah (13/131): It is permissible for the 
      agent to accept a fee of a known percentage of the final agreed price of 
      the product in return for telling the customer about it, and he may take 
      it [that fee] from the buyer or the seller, according to the agreement, 
      without any being unfair or causing any harm. 

    End quote.