Praise be to Allaah.
It is permissible to take commission in return for attracting customers and encouraging them to buy particular products, so long as the product is permissible, the commission does not add so much to the price of the product that it is damaging to the purchaser, and you try to be honest in telling the customer about the product. Taking commission on this basis comes under the same heading as brokerage.
It says in Fataawa al-Lajnah al-Daa'imah (13/131): It is permissible for the broker to take a known percentage of the price that is agreed to in return for showing it to him, and he may take it from the seller or the buyer, according to whatever has been agreed, on a fair basis. End quote.
It also says (13/130):
I took a customer to a factory or store to buy something, and the owner of the factory or store gave me commission for bringing the customer. Is this money (the commission) halaal? If the owner of the factory adds a particular amount of money for each item the customer takes, and I take this money in return for the customer buying this product, is this permissible? If it is not permissible, what is the kind of commission that is permissible?
Answer: If the manufacturer or trader gives you some money for every item that is sold through you, to encourage you to continue to look for customers, and this money does not increase the price of the product and that does not cause any harm to others who sell this product, meaning that this manufacturer or trader sells it for a price like that for which it is sold by others - that this is permissible and there are no reservations concerning it.
But if this money that you take from the owner of the factory or store increases the price of the product paid by the purchaser, then this is not permissible for you to take it and it is not permissible for the seller to do that, because this is harming the purchaser by increasing the price for him. End quote.
What we have mentioned as being permissible is just telling people about a particular product, without that being accompanied by what is called pyramid or network marketing, because that is a haraam kind of marketing, as is explained in the answer to question no. 42579.
And Allah knows best.