What is the ruling on selling cars through a broker who photographs and displays them, then the buyer pays their price and expenses along with a commission for the broker and another for the car owner, and is it a condition to inform the buyer of the amount of the commission?

Your mediation is called brokerage, and it is permissible to take a known fee for it. It is not a condition for the buyer to know the amount of commission taken from the seller, nor for the seller to know what is taken from the buyer.

Selling an absent item is permissible, with the option of rescission (khiyar) for the buyer according to some scholars, and this is the most preponderant opinion. The permissibility of selling an absent item relies on a prior viewing of the sold item that typically does not change afterwards, or on a complete description of it that removes any ambiguity. If the sent pictures fulfill this purpose according to experts, then they may be relied upon.

Paying the price in advance for an absent item as a voluntary act is permissible. However, if it is a condition stipulated by the seller or his agent, it is not permissible. If it is on the condition of an option (khiyar), then it is absolutely prohibited.