More than any one stock or mutual fund pick, the age you start investing will determine how much wealth you build. To illustrate: Employee A starts putting away $100 a month when she's 22. Her money grows at 8 percent a year, and after ten years she stops contributing - and lets her stake grow. Employee B waits until he's 32 to set aside $100 a month, also growing at 8 percent a year, and he keeps it up until he hits 64. When they both retire at 64, she will have $234,600, and he'll have only $177,400. Need we say more?