What is the ruling on taking a commission for purchasing goods for others online using a Visa card?

Purchasing an item for another person online for a commission is permissible if the transaction is an agency for a fee, meaning your friend sends the money first, and then you purchase the item. However, if you purchase the item with your own money and then they send you the money, taking a commission is not permissible because that is considered a loan that draws a benefit, which is forbidden usury (riba). Instead, you can purchase the item for yourself and then sell it to your friend for an agreed-upon price. This is called Murabaha for a party promising to purchase, and it is not permissible to take an advance payment from the customer at the promise stage.