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Alexandra Rutke was delighted when her son turned 18 months old. She could finally dig out her diaper bag and pull her neglected designer purse back out of her closet.

But when her family of three headed out for dinner in New York in August 2021, she realized she couldn’t cram wet wipes, snacks and emergency pull-ups into her sleek Saint Laurent crossbody. “I was so crazy about it,” Rutkay, now 41, says. “I thought, ‘There’s got to be something better for our mothers. Everything is so mean and stupid and nothing is cute.’

Rutkay is a full-time makeup artist who sometimes works up to 16 hours on film and television sets. Her side hustle, City Mouse, sells cross-body diaper bags with interchangeable straps. It launched in June 2022, and has brought in about $600,000 in revenue so far this year, according to documents reviewed by CNBC Make It.

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At first, Rutke didn’t tell her husband, David, about the city mouse, she says, because his attempts to stir her up from behind weren’t always successful. Now, he is the company’s only full-time employee, having taken a pay cut to run its operations, logistics and customer service. Rutke notes that collectively, the couple plans to pay about $150,000 starting this year.

Ratke herself works 40 hours per week on CityMouse — on top of her day job — because once she starts a project, she can’t let it go, she says. She is also more driven to build wealth, and eventually pass it on to her son, after a health scare: in 2020, she was diagnosed with a soft tissue sarcoma, a rare form of cancer, in her right thigh.

After surgery and chemotherapy, Rutke was deemed cancer-free in 2021. “Not to be desired, but if I had died before then. [my son] Even knowing me, what would I have left him?” she says.

Here, Rutkay discusses how others can follow her path, what she would change if she could start over and the most overrated business advice she’s ever heard.

CNBC Make It: Is Your Side Hustle Copyable?

Ratke: Yes and no. I think building a business that fills a need is the best possible way to grow and sustain a brand—many people can do it. But it takes a lot of luck to find that specific need for your project at the right time.

Consistency [of effort] is everything. I treated aspects of my past like hobbies, not businesses.

It is also important to know when the pivot is. When I started CityMouse, I took a six-week course with a spiritual life coach and realized I was feeling really bad about my previous failures. [side hustles]. It reminded me that knowing when to let go is actually a superpower.

How do you determine when it’s time to walk away from a side hustle when it’s not working?

I think the world just tells you. If you’re doing everything in your power to get your product or service out there through marketing, and people aren’t responding, that’s a clear sign.

After I had my baby in February 2020, I had the idea to make pizza themed baby milestone blankets. I invested about $6,000 from my previous Etsy shop, found a manufacturer overseas and launched it through Amazon’s FBA program.

It was my genius idea, and it was the biggest financial mistake I ever made. I didn’t spend money on advertising because I thought that if I listed with strong SEO, people would magically find it. That was not the case at all. Then, Amazon started charging me all these other fees.

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

If you could go back in time and change the way you launched CityMouse, what would you do to help it succeed faster?

I always thought I was my ideal customer, so I originally positioned CityMouse as a luxury brand for other city moms. It turns out, suburban moms who want to leave their big diaper bags in the trunk of their cars also need smaller bags for everyday errands like grocery shopping and Target runs.

It’s a big difference from anything else I’ve made. I’m very excited about CityMouse, and that’s because there’s an emotional element to it – for me and for other moms. I think finding that emotional element and figuring out how to make people feel something with your product is how you strike gold in business.

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

I know people say this out of the goodness of their hearts, but I can’t stand when you say you have an idea, and someone says, “You should go on Shark Tank.”

You don’t need outside investment to grow a profitable business. In fact, I would say “don’t do it.” I think there is so much beauty and less power in bootstrapping your company. You have full say on everything, you are making your own decisions. It is empowering.

That doesn’t mean I’m against it. [selling equity in your company] Forever in my wildest dreams, in the next five to seven years, I sell City Mouse and I start doing something else. I know people say don’t start a company with the intention of selling, but I know that myself. I am a serial starter. I might eventually want to pivot into a different line, a different product, a different industry.

But it would be nice to get out on top.

This interview has been edited and shortened for clarity.

CORRECTION: This story has been updated to reflect that Rutkay did not initially tell her husband about CItymouse because efforts to stir up his rear end were not always successful.

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