This story is part of CNBC Make It's Six-Figure Side Hustle series, where people with lucrative side hustles break down the routines and habits they've used to make money on top of their full-time jobs. Got a story to tell? Let us know! Email us at AskMakeIt@cnbc.com.

When Domonique Brown was little, she and her dad could only buy greeting cards featuring Black people at a single Hallmark store in Upland, California.

Now, the 30-year-old designs Black-centric greeting cards that line the shelves of Targets around the country. It's a "strange feeling," Brown says: When she started her art side hustle DomoINK in April 2020, she just wanted a way to share the art she made at her kitchen table — sometimes on her iPad or laptop, sometimes hand-drawn with markers and acrylic paint — in Jurupa Valley, California.

Months later, her business brought in enough sales on Etsy to cover the regular mortgage payments on her recently purchased house, Brown says. Partnerships followed: A year in, Target reached out and asked her to design a collection of prints and home décor for Black History Month, which launched in stores in February 2023. Since then, she's inked additional deals with Sharpie, Walmart, Airbnb and Disney.

Some of Brown's designs are licensed on art marketplace Society6, which means you can purchase items ranging from socks to credenzas bearing her art. Across all mediums and materials, her designs primarily feature Black characters and aim to represent the Black experience, she says.

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DomoINK made $333,600 in gross profits last year — an average of $27,800 per month — according to documents reviewed by CNBC Make It. Her business, still a side hustle, outearns her 9-to-5 job: She's a full-time graphic designer with a $90,000 annual salary, she says.

Brown typically spends two hours per day maintaining customer relations and creating content for DomoINK and, when inspiration strikes, creating new work, she says. Her past resume includes real estate and marketing jobs, giving her valuable sales experience, she adds.

At every stop, art has offered her a reprieve from schoolwork, unfulfilling jobs or people who told her to make more "white art," Brown says. Here, she discusses whether her business is replicable, how to build enough confidence to actually launch a side hustle and how she balances her creativity with her day job.

CNBC Make It: Do you think your side hustle is replicable?

I think so. If your brand is about representation like mine, you have to be able to speak to people, to network, so you can put yourself out there.

Education, technical skill and years [of experience] also give you an advantage. My first memories are in preschool, drawing portraits. I've always been an artist.

A lot of it has to do with believing in yourself, too, and not listening to people who say you can't [succeed].

How do you build enough confidence to convince yourself that you can make money at something?

If I went to a retailer, and [they said] "No," to my work, it made me think back to the past. I could hear somebody say, "Artists don't have real jobs. You should have went into health care."

You can use that negative energy to push yourself. When I worked in real estate, I had my artwork hanging around my cubicle, and somebody asked me, "Why do you only do 'Black art?' You would be so much more successful if you did 'white art.' You could do a portrait of Jerry Seinfeld."

It always stuck with me. After I quit that job, I always thought, "If I ever see him again, I want him to know my work is just as valuable as any other kind of art."

What do you think sets you, as an entrepreneur and artist, apart from your competition?

I know how to challenge myself. I think that's the best way to replicate success.

I started off doing portraits. When I started getting more brand deals, I learned how to design patterns because they looked better on rugs, towels and other textiles. I think that comes with my marketing background, wanting to educate myself on what's next and staying up-to-date on trends.

My family members inspired me, too. Both my parents worked at the post office and had normal 9-to-5s, but they had side hustles painting statues. My grandmother was a seamstress, and at 80 years old, was still designing and creating wedding dresses without patterns.

How do you approach maintaining a full-time job, a side hustle and time for your personal life?

When I first started DomoINK, I felt this huge pressure to create constantly because I didn't know if this was going to last forever. I took on so many projects, I wasn't sleeping, and I noticed my work was sliding.

Now, I think about life overall. I try to use my time more effectively, which includes sleeping and traveling. I don't work on the side hustle until after I'm done at my 9-to-5.

I also like to get out of business mode, and create in a way where this still feels like a hobby. My brand is about representation, so I'm always trying to design for the next person, or with a marketing strategy. But every once in awhile, I'll just create something that I know is just for me, that expresses how I feel in the moment, regardless of how it sells.

This interview has been edited for length and clarity.

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