A 17-year-old student who received $10,000 and used it to fund her Amazon side hustle now earns $71,000 a month.

Bella Lin spent an hour each week cleaning her two guinea pig cages by scraping, scrubbing, and power washing off excrement.

Lin, now 17, tells CNBC Make It that it was essentially a small portable toilet.

Lin created her own cages, starting with simple designs on notebook paper and eventually constructing them with bricks and plastic in her backyard in Sunnyvale, California. Now, she continues to produce these cages in a factory in Hangzhou, China.

Lin founded and runs GuineaLoft, a small pet accessory brand that sells on Amazon. GuineaLoft's cages are made with acrylic walls and a disposable wax-coated paper bottom, making them easy to clean. She launched the cages in November 2022 after about a year of prototyping.

This year, GuineaLoft has generated approximately $71,000 in monthly revenue, a significant increase from last year's average monthly revenue of $34,000 and monthly profit of $8,600.

Lin attributes her explosive growth to a single event: In October, she won $10,000 from a pitching competition at BizWorld, a project-based entrepreneurship program. She used the money to purchase an acrylic laser cutter, which significantly accelerated production times and ensured the availability of her signature cages.

Lin runs GuineaLoft as a side hustle, with six full-time employees responsible for product development, construction, and testing. Despite her recent high school graduation, she will soon enroll at The University of Chicago to study economics.

Lin talks about how she constructed her side hustle and her plans to sustain it as a college freshman.

Home-grown mentorship

Lin has been involved in various side hustles since childhood, including selling lemonade and hand-knit scarves, and was supported by her father, a computer programmer who had experience with start-ups.

Lin was taken aback by the high cost of Lululemon leggings while on her way to water polo practice. Her father inquired, "What do you think the markup is on these?"

TLeggings, another one of Lin's side hustles, brought in $300,000 at its peak in 2020. The pair discovered that most leggings made from the same fabric as Lululemon's cost around $20 to produce.

Lin believes that many parents tend to dismiss children's interest in start-ups when they are young and express it with trivial items like yarn or slime.

"My dad consistently regarded me as a mature individual, someone nearly collaborating with him."

Running GuineaLoft

In just over a year, GuineaLoft's signature cage went from prototype to being available on Amazon, with Lin listing 100 of them. The initial batch sold out in just two weeks.

GuineaLoft's Amazon storefront offers a variety of products for guinea pigs, hamsters, rabbits, and birds, including acrylic cages and accessories, hay feeders, and no-drip water bottles. The store's sales have increased due to the use of three acrylic laser cutters in manufacturing, increased marketing efforts, and an expanded product line.

Lin, a "veteran guinea pig owner," has faced challenges while gaining experience in designing cages and products for smaller pets.

Lin says that the company went through "at least five iterations" of its hamster cage. "To be completely honest … it got bad reviews," Lin says. Customers reported their hamsters were escaping, so GuineaLoft adapted its design.

'I'm kind of just the guinea pig girl'

Lin's friend circle outside of BizWorld lacks other entrepreneurs, and she describes herself as the "guinea pig girl" to them. She enjoys filling a unique role.

Lin's success can be attributed to finding her niche, which allowed her to innovate and fill a gap in the market with her first profitable business, GuineaLoft.

Lin is currently working 30 hours per week on her side hustle while enrolled in two college courses. Although she initially planned to take a gap year to focus on GuineaLoft, she now hopes to learn more and meet individuals who can potentially aid her in expanding the business.

Although Lin's company is profitable, she hasn't started paying herself a salary. She explains that her parents and a scholarship are covering her tuition at The University of Chicago.

Lin plans to open in-person stores soon, with the goal of making her products available on brick-and-mortar shelves.

"My objective for GuineaLoft is to become a well-known brand for small pets."

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