Simply parking most or all of your long-term investing dollars in a low-fee, broad-market index fund such as one that tracks the S&P 500 is a great way to invest -- and even Warren Buffett has recommended that strategy for most of us. Less those low fees, it will get you roughly the same return as the market (as measured by the index it tracks). Great, right?

Well, that is great, but the stock market has averaged annual returns of close to 10% over long periods, and over your investing time frame, it might return a bit more or less. If you crave faster growth, and you're willing to learn more about investing and take on more risk, you might invest a portion of your portfolio in some carefully chosen individual stocks.

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Image source: Getty Images.

Here are three contenders for your portfolio, each of which may double your money in just a few years -- or perhaps a bit longer. (The stock market offers few guarantees, and slumps can happen at any time.)

1. MercadoLibre

If you know a little Spanish, you might notice that MercadoLibre (MELI -1.18%) means "free market" -- so you won't be surprised to learn that it's an e-commerce enterprise. It's a big one, too, recently valued near $80 billion, and focused on Latin America. While $80 billion is a lot, it's still a far cry from the recent $1.6 trillion value of or the $658 billion value of China's mega e-commerce concern, Alibaba. And yes, while China is extremely populous, containing more than a billion consumers or potential consumers, the population of Latin America and the Caribbean is meaningful, too, at more than 658 million -- that's about twice the U.S. population. MercadoLibre has plenty of room for further growth.

MercadoLibre has been a good grower for a long time, gaining more than 1,800% over the past decade, and it has been innovative, too, capitalizing on opportunities. While starting out as more of an eBay-like business, it's now more like Amazon, and it has its own PayPal-like digital payment arm, too, in MercadoPago.

2. Redfin

Next up is Redfin (RDFN -1.83%), a relatively new business in the real estate market, founded just 15 years ago. Like Zillow, it lets homebuyers shop for homes online through its listings, and it sports its own team of real estate agents, too, who charge lower fees than mainstream realtors. (It notes, "Since our launch in 2006, we have saved our customers nearly $1 billion and we've helped them buy or sell more than 310,000 homes worth more than $152 billion.")

Like MercadoLibre, Redfin is also expanding its scope and reach, adding a mortgage and title business and buying RentPath to add apartment-hunting services to its offerings. (If you haven't heard of RentPath, perhaps you've heard of one of its sites, such as,, Lovely, and Redfin's RedfinNow service even buys homes directly from homeowners to resell.

Redfin has a lot going for it, such as a booming real estate market and a relatively attractive valuation. Consider, for example, that Zillow was recently valued near $38 billion, while Redfin is still near $7.9 billion. Redfin's recent price-to-sales ratio of 7.8 is likewise lower than Zillow's 9.9. This company appears to be well-positioned for further growth, with a management team ready and able to capitalize on opportunities that come along.

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Image source: Getty Images.

3. Teladoc Health

Finally, there's Teladoc Health (TDOC -2.45%), the telemedicine specialist that was soaring during the pandemic as more and more patients and doctors turned to virtual visits. The stock has retracted some recently, down about 35% from its 52-week high, but it has been performing well. The company's year-end results featured revenue nearly doubling to $1.1 billion, and total healthcare visits surging by 156% to 10.6 million. (Visits in the U.S. nearly tripled in number.)

Late last year, Teladoc expanded its scope by buying Livongo for about $18.5 billion. Livongo specializes in "applied health signals" and offers diabetes monitoring products, among other things. Its diabetes program pairs a glucose monitor with patient-coaching software, encouraging more activity, among other things. The U.S. is home to more than 34 million diabetics (more than one in 10 people) and some 88 million pre-diabetics. The company aims to expand into monitoring and addressing other widespread conditions, too, such as high blood pressure and obesity. Clearly, there is much more room to grow.

These are just three of the many promising businesses out there that deserve consideration for a berth in your portfolio. If any of them interest you, take a closer look.