From the Start, I Get a System That Gives Me a Thousandfold Cashback

From the start, he binds himself to a thousandfold cashback System that lets him multiply his money just by spending it! A poor young man unexpectedly awakens the System and starts buying everything in sight. For every yuan he spends, the System gives him a thousand yuan back! He can buy luxury cars and mansions at will, and beautiful campus queens chase after him. What happened to turn me from a down-and-out delivery rider into the richest man in the world?