Some investors like to buy stocks in "even" lots (more than 100 shares), which are easier to track and sometimes incur lower fees than smaller "odd" lots. However, it can cost a small fortune to buy even lots of certain stocks -- so some investors prefer stocks that trade at lower prices.

Today, a trio of our Motley Fool contributors will highlight three promising stocks that trade below $20 -- BlackBerry (NYSE:BB), Kinder Morgan (NYSE:KMI), and Codexis (NASDAQ:CDXS).

$20 bills.

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A solid second act for BlackBerry

Leo Sun (BlackBerry): BlackBerry once dominated the enterprise smartphone market, but the rise of iPhones and Android devices over the past decade destroyed its core business. However, CEO John Chen, who took the helm in 2013, pulled BlackBerry back from the brink of irrelevance by halting the production of its smartphones, licensing out its brand to a Chinese OEM, and focusing entirely on the growth of its software and services.

That turnaround was painful, but investors are now seeing the light at the end of the tunnel. Last quarter, its software and services revenue rose 10% annually on a non-GAAP basis and accounted for 96% of its top line on the same basis -- up from 85% a year earlier. Its total revenue still dipped 3% annually, but that broke its multiyear streak of double-digit declines.

For the full year, which ends on Feb. 28, analysts expect BlackBerry's revenue to fall 7% but its non-GAAP earnings (buoyed by its pivot to higher-margin software) to rise 21%. BlackBerry also expects to generate positive free cash flow for the full year. Looking ahead, analysts expect BlackBerry's revenue and earnings to rise 4% and 6%, respectively, indicating that its business is finally ready to move forward again.

BlackBerry still faces a lot of competition in the enterprise security and mobility software markets, and its stock isn't cheap at 45 times next year's earnings. Nonetheless, I believe BlackBerry still has room to run, and its stabilizing business, strong brand, and low enterprise value of $2.8 billion make it a lucrative takeover target.

An IT professional checks a tablet.

Image source: Getty Images.

Put some energy into your portfolio

Dan Caplinger (Kinder Morgan): Kinder Morgan has gone through a tough period over the past several years, as stubbornly low energy prices have largely kept the stock from recovering from the massive losses it suffered back in 2015. As a major pipeline operator, Kinder Morgan doesn't have direct exposure to falling prices for crude oil and natural gas. But its exploration and production company customers tend to base their production targets on energy prices, and when those prices are low, they're less likely to boost production -- thereby reducing the amount of energy products that Kinder Morgan has to transport.

However, there are some promising signs on the horizon. Kinder Morgan did finally produce modest growth during 2018, and the pipeline giant expects an even better performance in the coming year. With the expected completion of two expansion projects that will allow the transport of natural gas out of the Permian Basin to areas on the Gulf and East Coasts, Kinder Morgan could see dramatic improvements in cash flow that in turn could lead to a big increase in dividend payments. Given the stock's 4.4% current yield, the prospect for even more income has led to a big upsurge in share prices in 2019, and there could be more to come if Kinder Morgan executes well on its opportunities.

An up-and-coming biotech that will soon be profitable

Maxx Chatsko (Codexis): When living cells need to communicate, generate energy, or remove wastes, they rely on complex molecules called proteins. When proteins help to speed up a chemical reaction, they're called enzymes. And when enzymes are produced at industrial scale and used to manufacture everyday products more efficiently, they can make for an intriguing investment opportunity.

Codexis wields a technology platform for engineering enzymes for industrial and therapeutic applications. For over a decade, it has supplied enzymes to help some of the world's largest pharmaceutical companies manufacture active pharmaceutical ingredients in fewer process steps, with less waste, and at higher yields. In recent years, it expanded its expertise to food ingredient manufacturing and clinical diagnostics. Just last year, it initiated a clinical trial for an engineered enzyme that could one day treat a rare metabolic disease called phenylketonuria (PKU).

In other words, Codexis is an industrial biotech (pharmaceutical and food manufacturing) with a specialty reagents business (clinical diagnostics) that also happens to be developing its own therapeutic pipeline (PKU and others). Successfully scaling the platform has the business on the path to profitable operations and has begun to earn some respect from Wall Street. It's not too late for individual investors, though.

The diversified biotech has a few major catalysts to watch in the year ahead. In 2019, Codexis will begin supplying steady commercial volumes of an enzyme used to manufacture a new zero-calorie stevia sweetener from Tate & Lyle. The supply agreement should result in higher volumes of product and higher revenue and profit potential compared to pharmaceutical supply agreements. Additionally, Codexis is currently conducting a phase 1b trial to explore the safety of its PKU therapy when administered at high doses. Successfully completing that could earn it a hefty milestone payment from its partner, Nestle Health Science, and free up bandwidth to bring the next preclinical drug candidate into the clinic.

At a market cap of approximately $930 million today and the potential to exit 2019 with the ability to self-fund operations, Codexis may not be flying under the radar of biotech analysts for much longer.

Dan Caplinger has no position in any of the stocks mentioned. Leo Sun has no position in any of the stocks mentioned. Maxx Chatsko has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Kinder Morgan. The Motley Fool recommends BlackBerry. The Motley Fool has a disclosure policy.