The "best possible way" to make money is through a side hustle that generates $600,000 annually for a 41-year-old individual.

The Six-Figure Side Hustle series by CNBC Make It features individuals with successful side hustles who share their routines and habits for generating income in addition to their full-time jobs. If you have a story to share, please email us at [email protected].

When her son turned 18 months old, Alexandra Rutkay was thrilled. She could now leave her diaper bag behind and showcase her designer purses once again.

As she and her family of three headed to dinner in New York in August 2021, Rutkay realized she couldn't fit wet wipes, snacks, and an emergency pull-up into her sleek Saint Laurent crossbody. "I was so frustrated," she says. "I thought, 'There has to be something better for us moms. Everything is so bulky and unattractive and nothing is stylish.'"

Rutkay is a full-time makeup artist who sometimes works up to 16-hour days on movie and television sets. In her free time, she runs a side hustle, Citymouse, which sells cross-body diaper bags with changeable straps. The company launched in June 2022 and has already generated nearly $600,000 in revenue this year, according to CNBC Make It's review of financial documents.

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Initially, David, Rutkay's husband, opposed her starting the company because her past side hustle attempts were not consistently successful, she reveals. Currently, he is Citymouse's only full-time employee, taking a reduced salary to manage its operations, logistics, and customer service. Together, they aim to earn approximately $150,000 from the startup this year, Rutkay states.

Rutkay devotes 40 hours per week to Citymouse, a project she can't let go of, and is driven to build wealth to pass onto her son after a health scare in 2020 when she was diagnosed with a rare form of cancer in her right thigh.

Rutkay was declared cancer-free after surgery and chemotherapy in 2021. "If I had passed away before my son got to know me, what would I have left him?" she reflects.

Rutkay discusses her path, what she'd change if she could start over again, and the most overrated business advice she's ever heard.

CNBC Make It: Is your side hustle replicable?

Creating a business that fulfills a need is the best way to grow and maintain a brand. However, it requires a lot of luck for your project to meet that specific need at the right moment.

Consistency in effort is crucial. I treated my past side hustles as hobbies rather than businesses.

Taking a six-week course with a spiritual life coach helped me realize that I felt badly about my previously failed side hustles. She emphasized the importance of knowing when to walk away as a powerful skill.

What are the indicators that it's time to abandon a side hustle that isn't yielding results?

If your marketing efforts are not yielding results, it's clear that something is wrong.

I launched a pizza-themed baby milestone blanket through Amazon FBA's program after investing $6,000 from my previous Etsy shop.

My biggest financial mistake was my belief that my strong SEO listing would attract customers without advertising. However, I underestimated the importance of advertising, and my lack of investment in it led to my financial loss. Additionally, Amazon's additional fees added to my expenses.

I started panicking and liquidated the company four months after it started.

If I could go back in time and change the way I launched Citymouse, what would I have done to help it succeed faster?

I believed I was my ideal customer, so I initially marketed Citymouse as a luxury brand for city moms. However, I discovered that suburban moms who require a larger bag for daily errands like grocery shopping and Target runs also need a smaller bag for day-to-day errands.

The emotional connection to Citymouse is what sets it apart from anything else I've created, and it's why I'm so passionate about it. I believe that tapping into that emotional element and creating a product that evokes strong feelings is the key to success in business.

What's the most overrated business advice you've ever heard?

Although people often suggest it with good intentions, I dislike it when someone suggests I go on Shark Tank after expressing an idea.

Bootstrapping your business is the way to go. You have full control and make all the decisions yourself. It's empowering and doesn't require outside investments.

I'm not opposed to selling equity in my company forever, but in my wildest dreams, I envision selling Citymouse and starting something new in the next five to seven years. While some say not to start a company with the intention to sell, I know myself as a serial starter and I'm confident that I'll eventually want to pivot to a different line, product, or industry.

But it would be nice to exit on top.

This interview has been edited and condensed for clarity.

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