You'll often hear that the sooner you're able to start saving for retirement, the easier building a nest egg becomes. Funding an IRA or 401(k) in your 20s could conceivably give your money 40 years to grow before you need to start using it. In fact, if you contribute $3,000 to a retirement plan at age 25 and your portfolio grows 8% a year, which is a bit below the stock market's average, you'll be sitting on about $65,000 by age 65, even if you don't add another dime. And while you should aim for a larger ...