Building wealth doesn't have to be complicated. Buying leading businesses in essential sectors and aiming to hold them forever is a proven recipe for success over the long run.

From health insurance to life-saving medical treatments, healthcare is a sector that the world literally can't live without. Let's take a look at two well-established healthcare stocks that have made investors much richer in recent years and appear poised to do well moving forward.

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1. Eli Lilly: A best-in-class drug pipeline

With over 37,000 employees and products sold in more than 120 countries, Eli Lilly (LLY 1.96%) is among the largest pharmaceutical companies in the world. The drugmaker is most recognized for its mega-blockbuster type 2 diabetes drug, Trulicity. Among the company's other blockbuster products are its COVID-19 antibodies, immunology drug Taltz, and cancer drug Verzenio.

As a result of Eli Lilly's development of these products, a $10,000 investment in the stock just 10 years ago would now be worth a staggering $96,000 with dividends reinvested. For context, if you had made the same investment in the S&P 500, waited 10 years and reinvested the dividends, you would have made just $30,000. 

And thanks to Eli Lilly's impressive pipeline, there's reason to believe that the stock could perform almost as well in the next 10 years. The company's type 2 diabetes drug (and obesity drug candidate) Mounjaro could fetch as much as $25 billion in annual sales for Eli Lilly at its peak. And the immunology drug candidate for ulcerative colitis and Crohn's disease, mirikizumab, could become a blockbuster drug in its own right. 

Along with dozens of other projects currently in clinical trials, this is why analysts are expecting 19.1% annual non-GAAP (adjusted) diluted earnings-per-share (EPS) growth over the next five years. This is almost three times the drug manufacturer industry average growth projection of 7%. 

Eli Lilly's forward price-to-earnings (P/E) ratio of 39.8 is much more than the drug manufacturer industry average of 12.3. But based on the company's quality and blazing growth prospects, it deserves to be trading at its massive premium to peers. 

2. UnitedHealth: World's most dominant health insurer

UnitedHealth Group's (UNH -1.03%) $491 billion market capitalization makes it bigger than the next 10 U.S.-based managed care companies combined. The company's health insurance segment, UnitedHealthcare, served 54.6 million customers as of Sept. 30 while its technology health services business, Optum, served 101 million customers.

As a result of UnitedHealth's industry leadership, a $10,000 investment in the stock made 10 years ago blossomed into $116,000 with dividends reinvested. And as commanding of a lead as the company has in its industry, there is plenty of room for future growth. 

Market research firm Fortune Business Insights believes that the global health insurance market will expand from $2.1 trillion in 2021 to top $3 trillion by 2028. Factoring in bolt-on acquisitions and gains in market share, analysts forecast 14.2% annualized earnings growth over the next five years. For perspective, this is moderately superior to the healthcare plans industry's average annual earnings growth assumption of 12.6%.

And at a forward price-to-earnings (P/E) ratio of 21.3, UnitedHealth Group's valuation isn't that unreasonable compared to the healthcare plans industry average multiple of 16.8. This makes the blue-chip stock one that investors can buy with confidence