Do you know what millionaires say is the number one tool for building wealth? Is it single stocks? Nope. How about real estate? Guess again. What about an inheritance? Not even close.
The answer, according to our National Study of Millionaires, is the 401(k). In fact, eight out of 10 millionaires said investing in their employer-sponsored retirement plan—which included 401(k)s—was their main tool f…