Paraphrasing the late Senator Everett Dirksen, "A million here, a million there, and soon you're talking real money."

Becoming a millionaire is a life goal for many people that seems much too difficult to achieve to ever be a reality. But it's actually quite feasible, even for those of very modest means. What it requires, though, is a measure of discipline to save, defer spending, and invest.

Even small amounts contributed to a portfolio can grow to a million dollars if you start early and invest often in good companies that can grow over time. Here are three that might just help you achieve what may seem to be unattainable right now: the goal of being a millionaire retiree.

Mature couple high-fiving each other

Image source: Getty Images.

Amazon.com: The possibilities are endless

There is seemingly nothing that can stop the continued growth of Amazon.com (NASDAQ:AMZN). The e-commerce giant continues to add good fortune on top of its outsized potential, and racks up sales and profits that analysts anticipate continuing for as far as the eye can see.

eMarketer expects Amazon will account for almost 40% of all online sales this year, and though more competitors jump into the space every day, second place Walmart to have less than a 6% share.

Beyond just retail, Amazon's cloud business Amazon Web Services also continues to grow, achieving $11.6 billion in revenue in the third quarter. And while its very profitable for the online giant, AWS no longer has to carry the profit-generating weight by itself since its e-commerce operations have become very profitable in their own right.

This one-two punch is terrifying for most competitors. For example, Amazon's announcement that it's launching an online pharmacy -- a not unexpected development since it acquired PillPack -- sent shares of Walgreens, CVS, and Rite-Aid reeling. While not everything Amazon touches turns to gold, its track record is solid enough to cause established players to worry.

Innovative Industrial Properties: A REIT for the marijuana industry

No matter your position on marijuana, the legal weed industry is here to stay and will grow into a multi-billion opportunity as acceptance gains ground. As more states legalize marijuana, it becomes merely a matter of when, not if, the federal government follows suit.

Yet pot producers themselves have been a hit or miss proposition, which is why investors should take a look at Innovative Industrial Properties (NYSE:IIPR), a real estate investment trust that acquires indoor cultivation sites for medical marijuana operators and then enters into long-term leases for them.

It specializes in triple net leases, or those in which the tenant is responsible for paying the insurance, maintenance, and property taxes on the property. It generated $43.4 million in rental revenue in 2019, has increased that to over $76 million through the first three quarters of 2020, and analysts expect it to grow to as much as $280 million by 2023.

According to data from Arcview Market Research and BDS Analytics, legal marijuana sales in the U.S. are expected to grow from an estimated $12.2 billion in 2019 to over $31 billion by 2024, which means Innovative Industrial Properties has a long, green pathway for growth.

Teladoc Health: The right prescription for growth

There's no question the coronavirus pandemic aided the growth of Teladoc Health (NYSE:TDOC), which soared 150% in 2020 as physicians consulted remotely with patients during lockdowns. Consumers also appreciate the convenience of telehealth services, which no longer require sitting in a doctor's reception area to wait.

Its massive $18.5 billion acquisition of Livongo Health should bolster Teladoc's potential. Livongo collects data on patients and through artificial intelligence provides "nudges" to customers for personalized coaching to help control health issues. It began life as a diabetes management platform but has since expanded to cover high blood pressure and behavioral health.

The virtual care market is growing fast, and Teladoc is now a leading health technology giant after the Livongo purchase.

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.