Perhaps the best-kept secret when it comes to investing is that time¸ not cash, is the most important asset you can put to work for you. Just a little bit of cash, socked away for a long while, has the potential to grow into a substantial amount of wealth. Given enough time invested, even a person of modest means can retire with a million dollars or more.

This chart shows just how powerful of an ally time can be for someone targeting retirement at age 70 with a cool million, simply by earning the market's long-run 10% historical average returns:

Starting
Age

Monthly
Investment

Total
Invested

% of a Full-Time Minimum-Wage Salary

18

$47.24

$29,477.10

4.3%

21

$63.81

$37,521.83

5.8%

25

$95.40

$51,514.42

8.7%

30

$158.13

$75,900.37

14.5%

35

$263.39

$110,624.19

24.1%

40

$442.38

$159,257.65

40.5%

45

$753.67

$226,102.24

69.0%

50

$1,316.88

$316,051.95

120.6%

55

$2,412.72

$434,289.21

221.0%

60

$4,881.74

$585,808.84

447.2%

A teenager who can consistently sock away less than 5% of the salary from a minimum-wage job can retire a millionaire. On the flip side, even a well heeled 50-year-old who hadn't yet started saving for retirement would probably struggle with reaching that same milestone.

Small investments for real people
You might believe that with a mere $47 per month to invest, your money would get eaten alive by fees and commissions. In most cases, that might be true, but there's one class of investments that actively welcomes even small investments.

They're known as DRIPs -- dividend reinvestment plans. You might have to pay a small fee or come up with a bigger initial investment to join one. Once you're in the plan, however, many allow you to make additional contributions and reinvest your dividends with no fees or additional out-of-pocket costs.

Here are just a few companies that welcome the small investments that can help make millionaires out of ordinary folks:

Company

Initial Enrollment

Minimum Optional Contribution

More Information

3M (NYSE:MMM) 

1 share of stock

$10

Click here

Abbott Labs (NYSE:ABT)

1 share of stock

$10

Click here

American Electric Power (NYSE:AEP)

1 share of stock or $250 + $10 initiation fee

$25

Click here (opens PDF)

Kellogg (NYSE:K)

1 share of stock or $50

$25

Click here

Colonial Properties Trust  (NYSE:CLP)

1 share of stock or $200

$25

Click here (opens PDF)

Dow Chemical (NYSE:DOW)

1 share of stock

$25

Click here (opens PDF)

General Mills (NYSE:GIS)

1 share of stock

$10

Click here

Poverty is not permanent
The big barrier to creating a nation of millionaires isn't cash -- it's ignorance. DRIPs and other low-cost, low-barrier investment strategies are available to anyone who cares to seek them out. But if you don't know how money works and don't realize how important time is to securing your financial future, you won't get started until it's too late.

That's why The Motley Fool has teamed up with DonorsChoose.org to fund classroom projects that teach and improve financial literacy for students who are most at risk of falling through the cracks. Every time these programs reach a student, that student gets the valuable gift of time. And with that gift, he or she acquires the opportunity to move from poverty to prosperity.

You can change lives
Creating a nation of millionaires just might be as simple as improving financial literacy for children and then letting the power of time work its magic. It doesn't take much to make a huge difference. Every donation, no matter how small, is appreciated and goes directly toward the classroom project of your choice. If your donation doesn't completely fund a project, it's pooled with ones from other like-minded people, until the project is completely covered.

If you've ever wanted to make a huge difference in the life and future of a child, now's your chance to turn a small investment into a gigantic impact. Simply click here to see the financial-literacy projects that the Fool is sponsoring, and when you've found one you like, donate.

At the time of publication, Fool contributor Chuck Saletta did not own shares of any company mentioned in this article. Dow Chemical is a Motley Fool Income Investor pick. 3M is a Motley Fool Inside Value recommendation. Try any of our Foolish newsletter services free for 30 days. The Fool has a disclosure policy.