From rampant inflation to interest rate increases and supply chain disruptions, companies across nearly every sector are facing a unique set of challenges now.

However, when you're training your focus on quality businesses that you intend to buy and hold for at least three to five years -- if not much longer -- even the current pain investors are feeling shouldn't keep you from faithfully building your portfolio. 

If you have $2,000 to invest in stocks right now, here are two fantastic contenders to consider for your buy list. 

1. DexCom

DexCom (DXCM 0.49%) is one of the preeminent forces in the continuous glucose monitoring (CGM) device industry, controlling a roughly 50% share of this multi-billion-dollar space. 

The great advantage of DexCom's CGM devices is that users don't need finger sticks and can instead rely on a one-touch applicator paired with a small sensor and transmitter to keep track of their glucose levels. The latest generation of DexCom's CGM device -- the G7, which has been approved in Europe, U.K, and Hong Kong, and is currently awaiting approval in the U.S. -- is 60% smaller than its G6 system and is ready to use in half an hour instead of two. 

In the U.S. alone, it's estimated that 29 million people have been diagnosed with diabetes -- and another 9 million could have diabetes and not be aware of it. CGM devices allow individuals with Type 1 or Type 2 diabetes to keep track of their glucose levels on a 24/7 basis and potentially avoid a life-threatening medical event. It's no wonder that adoption of CGMs continues to expand at a rapid clip. 

By the 2028, it's estimated that the global CGM market will be worth $10.4 billion, as estimated in a recent report from Grand View Research. According to the same report, "Key factors driving this market are the rising incidence of diabetes, coupled with the increasing geriatric population prone to diabetes."

Over the past decade, DexCom has delivered a total return of nearly 300% for investors. This has been driven by the continued success of its CGM devices and robust revenue growth paired with consistent profitability. In that same trailing-10-year period, DexCom's annual revenue has increased 66%, while its net income has grown by more than 53%. In the first nine months of 2022, DexCom's total revenue jumped 20% compared to the same period in 2021, while its net income rose by a clip of 12%.  

At its current price, a $2,000 investment in DexCom would leave you with about 17 shares. 

2. Pfizer 

Pfizer (PFE) caught the attention of many investors in the earlier days of the pandemic. Comirnaty, the blockbuster COVID-19 vaccine that it developed with BioNTech, reached nearly $37 billion in sales in 2021. Its coronavirus antiviral medication Paxlovid hit $76 million in sales last year despite only gaining Emergency Use Authorization from the U.S. Food and Drug Administration in December.  

Now, with an inevitable decline in sales of Pfizer's coronavirus products expected, and some of its core products losing patent exclusivity soon, some investors might wonder whether the thesis for this healthcare giant still holds true. I would maintain that it does, and I'll tell you why. 

First of all, let's take a look at Pfizer's financial track record over a much broader period than its pandemic-era successes. It's true, balance sheet growth occurred at a much more conservative clip pre-pandemic -- not at all unusual for one of the world's largest pharmaceutical companies -- with revenue increasing by about 2% operationally in both 2018 and 2019.

However, looking back over the trailing-10-year period, the company has increased both its revenue and net income by around 50%, and its operating cash flow has risen by approximately 95%.  

While Pfizer reported revenue growth to the tune of 92% in 2021 (largely driven by its coronavirus vaccine and antiviral pill sales), excluding these products, revenue still jumped by a 6% clip compared to 2020. This is more on par with what investors would expect from a mature business like Pfizer's in a normal environment.  

In the most recent quarter, eye-popping performance in the year-ago period combined with a decline in coronavirus vaccine sales meant that on a year-over-year comparison, overall revenue actually decreased by 2%. However, taking out Pfizer's COVID-19 products, revenue actually grew 2% on a year-over-year basis. 

Pfizer is continuing to see strong growth from its existing broad portfolio of drugs, which include blockbusters like blood thinner Eliquis, its Prevnar family of vaccines, and cardiomyopathy drugs Vyndaqel/Vyndamax. As for its pipeline, CEO Albert Bourla noted in the third-quarter earnings report that "over the next 18 months, we expect to have up to 19 new products or indications in the market ... the majority were discovered in-house, and nearly all would be for indications outside of COVID-19."  

Pfizer's incredible successes with its COVID-19 products has also added a tremendous amount of cash to its balance sheet, which it has used to fuel its research and development pipeline and ramp up its M&A activity. Both strategies could pay off big time for its business over the next five to 10 years, and for investors as well.

In 2022 alone, Pfizer has made a series of well-placed acquisitions that have brought a range of promising candidates and therapies into the fold, including Arena Pharmaceuticals (known for its treatments for immuno-inflammatory disorders, among a range of other disease areas), ReViral Pharmaceuticals (known for its RSV therapies), and Biohaven Pharmaceuticals (known for its preventative migraine treatment). 

Beyond Pfizer's track record of blockbuster successes, another factor that may draw investors is its dividend. The healthcare stock features a yield of 3.4%, considerably more than the 2% of the average stock trading on the S&P 500. Pfizer's dividend has also increased by more than 80% over the past decade alone. To give context, Pfizer first started paying its dividend in 1938 (yes, you read that right), and has paid a dividend every quarter since. 

At Pfizer's current price, a $2,000 investment would add about 43 shares to your portfolio.