What is the ruling on selling a commodity that the seller does not possess, where an agreement is made with the buyer on its price, and then the seller agrees with the manufacturer on a price and pays the manufacturer after the buyer pays him an advance? And is this better, or should he work as an intermediary (broker) and take a percentage from the seller and the manufacturer, with the manufacturer calculating that percentage to the customer?

It is impermissible for a person to sell what he does not possess. However, it is permissible to display the type of merchandise, then acquire it, and then sell it to the buyer. As for the work of a broker (simsar), it is permissible and is considered under the category of ju'alah (a promised reward for a specific task). It is stipulated that the fee must be known, and it is not permissible for it to be a percentage of the profit according to the majority of scholars. There is also the Istisna' contract, which allows for an agreement to manufacture goods with specified descriptions.