It’s the era of the side hustle, and if you’ve ever considered starting one to earn some extra cash outside of your 9-5, you’re in good company. These days, more than one-third of U.S. adults have side hustles, and their supplemental gigs make an average of $891 a month, according to recent research from Bankrate. Of course, the most successful side hustlers see much higher earnings, especially when they start a business that brings in nearly as much as — or significantly more than — their full-time sources of income.
Jess Stern, 33, of London, England, is one of them. Read more about how she and her sister started and grew their business, here. Responses have been edited for length and clarity.
Image Credit: Courtesy of Mustard Made. Jess Stern.
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What was your day job or primary occupation when you started your side hustle?
I went straight into the corporate sector following school and spent 10 years working my way up the ladder as a buyer for big UK brands such as Primark and BHS. My background is very much in the mechanics of taking a product from concept to creation and then getting it out into the world. Becca, my sister and co-founder, has experience in small, creative businesses and entrepreneurship. She has always worked independently and previously created and built her own jewelry label, House of Bec.
Our professional experience was really different, but we could both see the challenges at each end of the spectrum. For us, Mustard Made, a homewares brand known for its colorful range of vintage-inspired lockers and organizational products, allowed us to create our own sweet spot in the middle.
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When did you start your side hustle, and where did you find the inspiration for it?
Becca moved to Australia in her early 20s, so living apart has really defined our relationship for the better part of our adult lives. That’s where the story of Mustard begins; in those years, we both shared a dream of starting a business so we could see each other more.
While I was on a trip to Australia to visit Becca and her new baby, we started talking more seriously about what a business might look like. Becca has always loved vintage lockers and had a few in her home and workshop that she had collected over the years. The lockers were beautiful, but never very practical in terms of the storage they offered. We both could see the opportunity to reinvent them as something that was both beautiful and functional, and that is where the idea for Mustard started. Fast-forward a few months, and we were in China meeting with potential manufacturers. Six months after that, we launched Mustard.
Image Credit: Courtesy of Mustard Made. Becca Stern, left, and Jess Stern, right.
What were some of the first steps you took to get your side hustle off the ground?
We launched Mustard Made at a trade show in Sydney, Australia. We used AUD 25,000 of personal savings to invest in samples, marketing and our stand at the show. The trade show was a huge success, and we walked away with over AUD 200,000 in orders, smashing our two-year projections in just one weekend. That was our very first lesson in business: Dream much, much bigger!
Related: This Couple Started a Side Hustle to Improve a ‘Terribly Made’ Bathroom Essential. Now the Business Earns More Than $3 Million a Year.
If you could go back in your business journey and change one process or approach, what would it be, and how do you wish you’d done it differently?
One of our philosophies at Mustard is to “Think 10x.” It’s basically asking ourselves, When Mustard is 10 times bigger than it is today, will this solution/technology/approach still be viable for us? It’s something we learned early on in our business journey when Becca was considering managing our product warehousing from a shipping container in her backyard. At that point, engaging with a third-party logistics provider felt like a huge step. Luckily, we did take the leap and sign on with our Australian 3PL because our ability to meet demand and scale the business would have been significantly restricted if we had attempted to manage our warehousing in-house. Thinking 10x and really backing ourselves has saved us so many headaches and allowed Mustard to grow and expand globally.
When it comes to this specific business, what is something you’ve found particularly challenging and/or surprising that people who get into this type of work should be prepared for, but likely aren’t?
The reality of being a founder is that we do new things every day, and every day we face new challenges and surprises. I like routine and knowing how to tackle something, so having to be okay with this has certainly kept me on my toes.
Just the other day, we had a customer receive a completely empty, fully sealed box of packaging from our warehouse. There was no locker or anything inside. In six years, we’ve never ever had this happen, so it completely stumped us! That’s a small bump in the road in the scheme of things, but we’ve had everything from the Suez Canal blockage stopping our stock from moving, to fires on container ships, to Covid-19 — these are all things we just couldn’t have prepared for. But that’s also part of what makes this job so rewarding. You have to embrace the unknown because we’re doing something we’ve never done before. As the team has grown, it’s been so great to have people on the ground in the UK with me, instead of me waiting 12 hours for Becca to be up!
Related: This 17-Year-Old High School Student Has a $20,000-a-Month Side Hustle — and It All Started With a Skill He Learned in Class
How long did it take you to see consistent monthly revenue? How much did the side hustle earn?
From the time that we launched Mustard at our first trade show in Australia, Mustard has grown consistently. I spent the next six months working on it as a side hustle, calling Becca on my way to and from my day job so we could check in with each other as my day was ending and hers was beginning, or vice versa. But after six months, I went all-in on Mustard, launching the brand in the UK and leaving my corporate career behind me.
Image Credit: Courtesy of Mustard Made
What does growth and revenue look like now?
Since launching in 2018, we’ve grown Mustard from a startup into a thriving global brand, now spanning three continents and supported by a team of over 30. 2024 marked a record-breaking year for Mustard Made. In 2023, the United States was our second-smallest region, but in just 12 months, it became our largest with 116% year-over-year growth in the U.S.
Overall, our business saw 46% growth globally in 2024, with revenue crossing eight figures. The U.S. represented 29.5% of our total market mix in 2024, up from 20.7% in 2023, and we’re now predicting that by the end of 2025, the U.S. market will surpass both the UK and Australia combined. Additionally, the number of lockers sold in the U.S. doubled from 2023 to 2024, underlining the strong momentum and continued success we’re seeing in the region.
What do you enjoy most about running this business?
Working with my team is my biggest joy. I love working closely with others, and a big turning point for me was when I made my first two hires. We were actually only hiring for one role, and I found myself trying to choose between two absolutely incredible applicants. In the end, I decided to back myself and hire them both, trusting that Mustard was only going to keep growing. Thirty hires later, I’m so glad I did!
I love to see people grow and blossom, and I love promoting staff and watching them thrive. I know I’m not necessarily the best or most knowledgeable in the room, so I love bringing on people who are the best in their field and taking their feedback on to help us grow.
Image Credit: Courtesy of Mustard Made
Related: This Former Microsoft Consultant Started a Side Hustle After a Frustrating Vacation Experience — It Hit $250,000 Fast and Makes Millions Now
What is your best piece of specific, actionable business advice?
As I mentioned earlier, asking yourself What would we do if we were 10 times bigger than we are now? is the best advice I can give anyone. It forces you to consider and invest in the scalability of your business.
Sourcing advice and sharing our experience is something I am trying to do more of, and next month I have a first meet-up with a founders’ network group based in London. I am looking forward to being part of a group of people who have been there before or are going through it.
