Is it permissible to take a commission from the seller, the buyer, or both, and is it permissible to share a commission with a third party from one side (e.g., the seller) while taking a full commission from the other side (the buyer)?

It is permissible for the broker to take a commission from both the seller and the buyer, unless he is an agent for one of them. In that case, it is not permissible for him to take a commission from the other party except with the consent of his principal.

If several brokers participate in the brokerage, and they are responsible for concluding the contract, then scholars have differed on the validity of this partnership. However, if their participation is in promoting the commodity, bringing customers, and similar activities, then the partnership is valid. If a broker seeks the assistance of another broker for a fee, this is permissible and falls under the category of ijarah (leasing/hiring) or ju'alah (a reward for a specific task).