The Buy Multiplier is a useful tool that allows you to buy more than one business at a time. It starts out saying "Buy x1", but you can click it, and it turns to Buy x10. You can click it three more times to get Buy x100, Buy Next and Buy Max. Buy Max buys the maximum you can afford when you click an item and Buy Next buys the amount needed for the next unlock. If you click it again, it will loop back around to Buy x1.