Richard S. Ruback and Royce Yudkoff, professors at Harvard Business School, spell out an overlooked career path: buying a business and running it as CEO. Purchasing a small company lets you become your own boss and reap financial rewards without the risks of founding a start-up. Still, there are things you need to know. Ruback and Yudkoff are the authors of the “HBR Guide to Buying a Small Business.”