The first half of 2021 was a strong one for the overall stock market, with the Dow Jones Industrial Average, S&P 500, and Nasdaq Composite benchmark indices producing total returns of 14.1%, 16.5%, and 14.2%, respectively. However, the rally hasn't exactly been universal – for the most part, value stocks have outperformed and high-growth stocks have lagged the market.

With that in mind, it's a smart idea for long-term investors to look for bargains in their favorite companies when a certain part of the market takes a hit, so that's what I've been doing recently. Two stocks in particular that I've been adding shares to my positions recently include MercadoLibre (NASDAQ:MELI) and Boston Omaha Corporation (NASDAQ:BOMN). Here's why I'm confident enough to double down on them, even though both have underperformed the market so far in 2021.

Finger pressing red button labeled buy.

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Massive untapped potential

MercadoLibre is often referred to as the Amazon.com (NASDAQ:AMZN) of Latin America, and for good reason. It operates an e-commerce platform that has a dominant presence in several key markets in the region, such as Brazil and Argentina. And the business is thriving – MercadoLibre recently reported gross merchandise volume (GMV) growth of 114% year over year in the first quarter. Over $6 billion in products were sold on the platform in the first three months of 2021.

Remarkably, this is the less impressive of the two major components to MercadoLibre's business. It also operates a payment platform known as MercadoPago, which processed $14.7 billion of payments in the first quarter, which was a 129% growth rate over the same quarter in 2020.

One thing investors need to keep in mind is the massive market potential. Many of MercadoLibre's core markets are in much earlier stages of e-commerce adoption than the United States. And although the growth has been very impressive, it's worth pointing out that MercadoLibre's marketplace sales volume is roughly 4% of Amazon's and Mercado Pago's payment volume is about 6% of PayPal's (NASDAQ:PYPL). In a nutshell, this isn't just investing in the "Amazon of Latin America" as you'll often hear MercadoLibre referred to. It's like investing in the Amazon, PayPal, and maybe even the eBay (NASDAQ:EBAY) of Latin America at much earlier stages of their respective growth stories.

An emerging conglomerate that could be a big winner for early investors

Boston Omaha is one of those companies the market doesn't really know how to value. And that could be a very good thing for long-term investors.

Often compared to an early stage Berkshire Hathaway (NYSE:BRK.A)(NYSE:BRK.B) because of its investment style, Boston Omaha is a conglomerate with three core businesses – billboard advertising, insurance, and rural broadband internet service. These businesses can have great economics, especially as they scale. For example, rural broadband requires little ongoing investment after the infrastructure is put in place, and already runs an 86% gross margin for Boston Omaha despite its relatively small size.

In addition, Boston Omaha invests in minority stakes in businesses, as well as in common stock positions, which is why its conglomerate style is more like Berkshire's than traditional operators. And it has been very successful. One particular home run is Boston Omaha's 5% stake in Dream Finders Homes (NASDAQ:DFH), a roughly $100 million position for which the company paid just $10 million a few years ago.

Finally, Boston Omaha is one of the only publicly traded SPAC sponsors you can invest in, and perhaps the only one whose SPAC has true needle-moving potential. Its Yellowstone Acquisition (NASDAQ:YSAC) is still looking for a company to take public, and regardless of what you think of the "SPAC boom," one thing is certain – the economics are highly skewed in favor of the sponsor. If Boston Omaha finds a good target to take public through Yellowstone, the value creation potential is huge. With a market cap of less than $900 million, now could be a great time to get in on this "baby Berkshire."

Neither of these are low-risk

As a final thought, it's important to emphasize that I don't consider either of these to be low-risk stocks, especially in terms of short-term volatility. While I believe both offer excellent value at their current prices, they can (and probably will) take investors for quite a bit of a roller-coaster ride along the way. Invest accordingly.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.