Many materials sold by Material Network are actually owned by others and have no copyright.
If you are sure that you are buying copyrighted materials, then according to the agreement you signed when you bought them, there will be provisions on whether they can be used for commercial purposes or for resale.
I usually buy empty shots and other materials on the program purchase website, and I can directly scan the code to pay. It's very convenient. More importantly, when I buy it, I will sign an agreement, clearly indicating that the materials I buy are copyrighted and can be re-created and re-commercialized. This way I can use it more safely.