You don't need the investing acumen of Warren Buffett or the riches of a trust fund baby to achieve financial success. Small sums of money invested monthly in undervalued small-cap stocks offer the best growth opportunities, because they're mostly ignored by the big investors.

Below, we screen for stocks with less than $3 billion in market cap, offering earnings surprises of 15% or more in the previous quarter, with a long-term earnings growth forecast of at least 15%. We'll then filter our findings through the collective investing wisdom of the 170,000 members in our Motley Fool CAPS community.

Here are some of the stocks this simple screen found:

Company

Market Cap

EPS Act. vs. Est.

Avg. Analyst 5-Yr EPS Est.

CAPS Rating

LDK Solar (NYSE: LDK)

$1.5 billion

$1.09 vs. $0.92

25%

***

NutriSystem (Nasdaq: NTRI)

$417 million

($0.12) vs. ($0.30)

17%

***

St. Joe (NYSE: JOE)

$2.4 billion

($0.06) vs. ($0.09)

15%

*

Source: Yahoo! Finance and Motley Fool CAPS.

Of course, this is not a list of stocks to buy -- just a starting point for more research. We need to look more closely at these companies to see whether analysts' faith in them is well-founded.

An alternative opportunity
China solar shop LDK Solar may have enjoyed forecast-beating results last time out, but its just-announced first-quarter guidance rained all over the expectations parade. LDK expects revenue to come in at $755 million at most, a 5% to 10% drop from previous estimates.

While those headline numbers helped push the stock down, the rest of LDK's guidance was something of a mixed bag. Wafer shipment forecasts were tightened, with the low end raised but the top end falling. The company predicted a drop in module shipments and a boost in in-house polysilicon production. LDK also expected its gross margin to exceed previous estimates.

The lower guidance does not occur in a vacuum, though. Other solar plays are stumbling because of the glut spread out over the industry. Both ReneSola (NYSE: SOL) and Evergreen Solar (Nasdaq: ESLR) disappointed investors, too.

The one bright spot was SunPower (Nasdaq: SPWRA), but only because French energy company Total agreed to pay a big 46% premium for a majority stake in the solar company. Total said it would pay up to $1.37 billion for 60% of both SunPower's class A and class B shares.

You can still shine a light on your views over on the LDK Solar CAPS page.

What system is that?
No one's been getting fat off of NutriSystem lately, after the weight-loss leader said sales would go on a restrictive diet. Anecdotal evidence speaks to the lack of appetizing fare among its food offerings, and even management says it needs to come up with something new. It's hard to really want to feast on this stock after that, even though it's trading 37% below its 52-week high.

In contrast, investors have been gorging themselves on rival Weight Watchers (NYSE: WTW), sending its shares to new highs and tripling in value over the past year.

CAPS member miksong says NutriSystem won't be bringing investors to the land of milk and honey anytime soon:

New customer starts have fallen like a knife and this has a circular effect on demand later on as much is circulated through word of mouth. Additionally, about 25% of the company's revenues come from previous users that decide to reup. This universe also now decreases.

Not willing to take a seat at the NutriSystem table? Add the stock to your watchlist to see whether it gets any more appetizing.

Man the ramparts
With its development properties located primarily in the Florida panhandle, St. Joe has been particularly hit by the depressed housing market. However, it's wriggled its way past much of the calamity by adopting what it calls a "place-making" strategy: making construction-ready investments in roads, pools, and golf courses for its properties, which it then sells to developers for home construction.

In an epic battle over whether the real estate developer would survive, famed value investor Bruce Berkowitz launched a buying blitz, snapping up large swaths of the company. At the same time, short-selling hedge fund operator David Einhorn said the company was dead because "it can't build, it can't sell, and it can't generate value to cover the operating costs."

Berkowitz seems to have won on all accounts. He wrested control of the company from management, got installed as chairman of the board, and has presided over the stock's resurrection. Shares are 20% higher than where they started the year.

Though more than half of the 200 CAPS All-Stars rating this stock still expect it to sink, you can develop a bull case for the company on the St. Joe CAPS page.

Foolish final thoughts
Stock investing is not brain surgery. Finding good, undervalued companies is not as difficult as the professionals want you to think. You just have to commit to starting now, and do so regularly. Now's the time to begin!

Total is a Motley Fool Income Investor choice. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. 

Fool contributor Rich Duprey does not have a financial interest in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.