From everyday Americans to celebrities, doomsday preppers are stocking up for fears of the end of the world, nuclear war, a major economic collapse or World War III. Now, real estate speculators say there are plenty of people concerned about the future to buy properties in bunker communities. Doomday prepping has been defined as: "The management of stockpiled household items in anticipation of market disruption." Preppers are people who make preparations to survive without government assistance in the event there is a disaster. They may learn survivalist skills as well as stockpile supplies such as food and ammunition. In the past year, Finder.com says 39% of millennials and 40% of those in Generation Z reported spending money on prepping. [Vivos xPoint is] a former Army base turned bunker community in South Dakota that's off-grid and built to be self-sufficient. Some people have a plane full of gas to get them to their bunkers at any moment. Some of the bunkers have generators, a bomb blast door, gun safes, an electrical room and storage for food, along with bedrooms and bathrooms. The South Dakota property of more than 530 bunkers is built to be self-sufficient. Out of all the $55,000 bunkers on site, about 200 have sold and sales have been picking up. Many countries in the world, including the U.S., advise people to prepare to survive for three days without assistance from authorities in the case of an emergency.