Billionaire super-investor Warren Buffett has shared plenty of financial wisdom over his almost 70-year career. When addressing the subject of retirement planning, he famously said, “If you don’t find a way to make money while you sleep, you will work until you die.” Consider This: 15 Investments Warren Buffett Regrets Learn More: 6 Popular SUVs That Aren't Worth the Cost -- and 6 Affordable Alternatives In other words, without enough passive income (or enough savings to “pay” yourself), you’ll never be a ...