Copyright/Trademark infringement?

So, I want to make a custom superhero shirt, with all of my favorite superheros on it. I thought about the whole copyright thing, so I looked it up and I'm a little fuzzy about how it works. Do I need to have the owner's permission to use them since I am buying the t-shirt after it is made from a store (money being made thing)? Or is it continuous money and sales they care about?