Your kid comes to you with a business idea. They're excited. They've done some planning. They even know how much they'll charge. But here's the question nobody's asking: Is this actually a smart use of their money? Not "Will they make money?"—that's easy to figure out. The harder, more important question is: "Will they make enough  money to justify what they're spending?" That's what ROI tells you. Return on Investment. And it's possibly the most powerful number your kid will