Live in Peace in the Prosperous Times, Make Money in the Last Days

Zombies broke out and the system descended. People all over the world liked to bring up "task panels" to fight monsters, upgrade, and receive rewards. The end of the world seemed to have become an immersive game in which everyone participated. Li Xiangfu, a veteran, squats at home, and stays flat in the prosperous times. Facing this trend, he was pleasantly surprised to find that he had indeed been selected by the system! However, when someone else's system releases a task, his system only pops up a shopping interface. [This system supports the exchange of items for gold coins, and gold coins can be used to purchase everything in the mall. [Current balance: 54250.00 (From your life savings)] Li Xiangfu: "???" Watching the new equipment and supplies that others continuously obtained after completing their missions, automatically put on the shelves in his store, but marked with staggering prices... Li Xiangfu fell into deep thought. Other people's systems provide resources, but he has a mall that can't produce anything? Doesn't this force him to become a black-hearted merchant?