I’m looking forward to buy a used apple laptop for under $400. As a vivid windows user (that is what i have been using my whole life!), I rarely know about the apple os. For windows based computers, i know that it is cruicial to get the copy of the os and the product key for it. I just want to know if apple does the same thing, so i can question for it when im buying. if so, please tell me where the product key is so i dont get hustled! thanks