Is the method of earning a livelihood that involves designing images to be printed on goods the designer does not own, and then a website sells and manufactures them after purchase, with the designer receiving a commission, permissible (halal) or forbidden (haram)? And does it fall under the Hadith: "Do not sell what you do not possess"?

If the one designing the drawings does not sell the goods but takes a commission for the design, or if he is a partner with someone who manufactures and sells the goods, then this is permissible.

However, if he sells the goods before owning them, this is not permissible. But it is permissible for him to act as an agent for the seller for a known fee, or to promise the buyer and then purchase the item and sell it to him.

It is also permissible to sell something described but not specifically designated, provided that a delivery date is specified and the price is paid in advance at the contracting session.