BUY NEXT DOOR | 274 followers on LinkedIn. Lacking something you need? Simply knock on their door, and buy it from your next-door neighbors | Buy Next Door is a coming of age e-commerce startup that caters to college students. College students often need a lot of things that they do not have, and they have a lot of things that they do not need. Our mission is for the things to go into the right hands, to the people that need them.