the Fatwa Department Research Committee - chaired by Sheikh `Abd al-Wahhâb al-Turayrî
All of these means of doing business are lawful as long as the goods and services involved are lawful in and of themselves and as long as no fraud or deception is engaged in.
The first case is a straightforward case of selling a product for someone else and taking a commission. This is a normal accepted business practice in Islamic Law.
The second case is taking a commission on goods bought by someone who is brought to the seller by a referring agent. This is also a quite straightforward practice.
The third case is comparable to being paid for the service of bringing someone to a certain venue. Here, you are being paid for the service rendered and not a commission on the goods and services sold. It is like someone working in a town as an agent for a hotel or a shop who takes people by the hand and leads them to that venue. For each person the agent leads to the venue, he gets paid a fixed amount for the service that he has rendered, regardless of whether the person brought to the place purchases any goods or services. Again, it is a quite straightforward business relationship.
And Allah knows best.
Source: Islam Today