It takes 9.5 years to save $100,000 if you're putting away $650 per month at an average 7% annualized return. Legendary investor Charlie Munger, Warren Buffett's longtime business partner at Berkshire Hathaway Inc. (BRK.A, BRK.B), understood the psychology of wealth building better than most. The Brutal Math of Building Your First $100K"You start saving early in your career—a few hundred dollars here; a few hundred dollars there. And despite compound returns, it adds up painfully slowly," says Hilary Hendershott, president and chief advisor of Hendershott Wealth Management. Only after you cross this threshold will your money start to work for you.