Postcards (as high as $4,400)

Collecting postcards can prove to be worth your while. So don’t forget to purchase postcards if you walk past a box of postcards that are for sale next time. You could rake in up to a whopping $4,000 just for a thick piece of paper — of course, it should be signed by Prince Charles and Diana, or other famous people in history for that matter. We think it’ll be worth the investment money, though.

The earliest known picture postcard was created by the Englishman writer, Theodore Hook. It was a hand-painted design on a card. In the late 19th and early 20th centuries, postcard productions became a convenient and easy way for people to communicate with their loved ones and they eventually became popular the world over.