Collecting doesn't always have to be expensive, but sometimes cashing in can be good. As an example - think cereal boxes. They're just packaging when purchased, you ate the cereal and threw away the box. Unless that is you saved those unusual boxes from your cowboy heroes or cartoon characters. I recently updated the page with cereal box prices and was surprised at some of the prices from recent auctions. Over $500. each for a Cheerios Lone Rangers, a 1970s Quisp and a 1970s Quangaroos (?) box.
Today's boxes will most likely not reach those figures, but those entertainment related boxes that are out for only limited time could be worth a few bucks down the line. Best of all cereal boxes do not have to have contents in them to sell - collectors empty and flatten them, great for the space challenged.