We'd all love to be millionaires (unless we're already billionaires, of course) -- but many of us assume that it will never happen. Don't sell yourself short, though, because for many people, achieving millionairehood -- and locking in long-term financial security through the end of retirement -- is much more possible than they thought.

Better still, becoming a millionaire doesn't have to require lots of work. Indeed, your money can grow and grow while you sleep! Here, in honor of National Napping Day, which happens to be March 15, are three ways to get wealthier while you sleep.

A man is sleeping, clutching hundred-dollar bills.

Image source: Getty Images.

No. 1: Use the power of time

Glance at the table below and you'll see that if your money is growing at 8% annually, you can achieve millionairehood whether you invest $10,000 annually, $15,000 annually, or $20,000 annually. A key difference, of course, is that you can get there much faster if you invest greater sums -- it might be accomplished in only about 20 years. That can seem like a long time, but if you're 35 now, that could provide enough to retire early with, at age 55 or soon after. And if you're 45, it can beef up your savings and give you more financial security at retirement.

Note the power of time in the table: The longer you have to save and invest, the more you can amass, even with relatively small regular investments. So make good use of all the time you have until you retire -- and consider adding a little more time, by possibly retiring a few years later than planned. Once your dollars are deposited in solid long-term investments, they will grow day and night -- even while you sleep.

Growing at 8% For...

$10,000 Invested Annually

$15,000 Invested Annually

$20,000 Invested Annually

5 years




10 years




15 years




20 years




25 years




30 years




No. 2: Invest effectively

Next, notice that 8% assumed growth rate in the table above? That's there in order to be a little conservative, because the stock market's long-term growth rate is close to 10%, but it can be much higher or lower during your own investing timeframe. The table below shows what a difference the growth rate makes:

$10K Growing For...

At 6%

At 8%

At 10%

10 years




15 years




20 years




25 years



$1.1 million

30 years


$1.2 million

$1.8 million

35 years

$1.2 million

$1.9 million

$3.0 million

40 years

$1.6 million

$2.8 million

$4.9 million

On a chalkboard, a graph of time and money leads to growing value.

Image source: Getty Images.

So don't just keep your money in low-yielding accounts, bonds, or funds -- or in stock mutual funds that aren't growing at a good clip. Don't count on gold to be a strong long-term performer, either. Check out the table below, based on data from University of Pennsylvania professor Jeremy Siegel, who studied returns of various investments over more than 200 years:

Asset Class

Annualized Nominal Return, 1802 to 2012









U.S. Dollar


Source: Stocks for the Long Run, Jeremy Siegel.

For long-term investing, the stock market is likely to be your best choice, and a fast and simple way to invest in it is via low-fee, broad-market index funds, such as ones that track the S&P 500 or the total U.S. or world stock markets.

No. 3: Use the power of dividends

Another great way to have dollars piling up in your investing accounts while you sleep is to invest in solid dividend-paying stocks or dividend-focused ETFs. Most dividends are paid quarterly and just appear in your brokerage account every few months -- and dividends from healthy and growing companies tend to be increased over time, too. That dividend growth can help you stay ahead of inflation, and when paired with stock-price appreciation over time, it makes for a nice one-two punch.

If you have a portfolio of, say, $400,000 spread across some strong dividend-paying stocks with an average yield of 4%, you're looking at $16,000 in annual income in your first year alone -- about $1,333 per month on average. If that payout rises by just 5% over the next decade, it will become $26,000 per year, or more than $2,000 per month.

An average yield of 4% isn't that hard to find, either. At the time of this writing, pharmaceutical company AbbVie (ABBV -0.76%) yielded 4.9%, while IBM (IBM 0.13%) yielded 5.3% and AT&T (T 0.17%) yielded 7.2%.

There are multiple ways to invest so that you get rich while you sleep -- and while you work at your job and play with your kids and go to the movies. Develop a saving and investing plan so that you can reach your financial goals.