I've interviewed dozens of self-made millionaires, early retirees, and 'super savers' and plan to use one of their top wealth-building strategies in 2025

• After years of writing about financially independent individuals, I've picked up on commonalities.
• One is that they have multiple revenue streams — at least one of which is from their own business.
• In 2025, I'm starting my own side business to see if the wealth-building strategy works for me.

My job involves interviewing people who are good with money — self-made millionaires, early retirees, and "super savers" who keep the majority of their income — and asking them to share their wealth-building strategies.

After nearly a decade of talking to these money-savvy individuals and absorbing their knowledge, I've implemented a lot of what they advise: I automate my savings and investments, live within my means, track my expenses and net worth, and take advantage of an HSA.

I have a lot of the personal finance basics down, but in the spirit of a new year and always trying to improve, I've decided to think bigger for 2025 and tackle one particular wealth-building strategy I've written about but never dared to try: starting a business.

One observation from talking to financially independent individuals is that they don't rely on a single source of income. They have at least two and, oftentimes, multiple revenue streams. Even the super savers tell me that there's a cap on how much you can save. But how much you can earn, they point out, is limitless.

Another commonality is that one of their revenue streams comes from their own business.

I've spoken to Amazon and Etsy sellers who have built e-commerce empires, content creators who drive passive income from courses and affiliate links, and a millennial who went from broke to seven figures by building websites and flipping domains.

Starting an e-commerce business

The business model that most intrigued me — and seemed doable on a budget — was e-commerce. Essentially, selling a product on platforms like Amazon.

I learned through interviews that there are three main ways to make money on Amazon.

There's arbitrage, which is the most basic, low-cost way to start selling on Amazon. This is when you source products from different marketplaces to sell. To be profitable, you must buy the product for less than it sells on Amazon. After reselling, you keep the difference.

The next tier is wholesaling. This is when you buy products in bulk and resell them on Amazon. Like arbitrage, you aren't making your own product — you're simply reselling an existing product — but you're spending more money upfront on inventory.

Finally, there's the private label route. E-comm experts have explained to me that starting a private label brand is the most time-consuming and costly but has the most upside. It requires actually creating a product and brand.

I went with the latter and technically started the company in 2024 when a friend and I designed a pickleball paddle and ordered inventory from a manufacturer in Asia. My goal in 2025 is to sell the 500 paddles that are on their way from China to my apartment in LA, build a brand I'm proud of, evaluate whether selling a product online is a suitable side hustle for me and my strengths, and write about every step of the process.

I don't expect building a side business to be easy. And everything I've done so far has cost more and taken more time than anticipated.

Most of the financially independent entrepreneurs I've spoken to started with a side hustle — and, in some cases, simply a side project or hobby that cost them money, let alone brought any in. They put their heads down from 9-to-5, worked for an employer to cover their bills, and then reserved 5-to-9 for building businesses.

Carving out time and energy to work on a side project that might not generate sales while simultaneously working a full-time job isn't for the faint of heart. These self-made entrepreneurs put in a lot of hours for an unknown outcome.

NeuroGum cofounder Kent Yoshimura, who worked at a music studio and as a muralist while building a caffeinated gum and mint company, admitted to pulling "an all-nighter once a week" in the early days of his startup.

Jatz Naran said he built his Amazon business between the hours of 6-and-10, after his day job would wrap up. "Forget work-life balance," he told me. At the end of the day, "you have to sacrifice one thing for another."

What's intriguing about starting a business is that you're in the driver's seat. The success or failure of the company is up to you. How much you and the company earn is up to you.

I'm reminded of something real-estate entrepreneur Dion McNeeley told me during an interview: Think beyond your day job.

His revenue streams at the time included his day job running a commercial truck driving school, long-term rental income from his portfolio of 16 properties, and a side hustle as an expert witness, which is someone who is called to testify during a trial because of their specific knowledge. He provided expert testimony for cases involving truck driving accidents.

"I make way more money spending two hours a month on real estate and one to two hours a month providing expert testimony than I make running a truck driving school," said McNeeley, who has since retired from his day job. "The mistake a lot of people make is selling their lives one hour at a time and not realizing that you make a lot more money when you get paid on the value you produce."