At age 12, Bella Lin spent an hour every week "scraping, scrubbing and power washing" excrement off her two guinea pig cages. This year, GuineaLoft has brought in roughly $71,000 a month in revenue so far, according to documents reviewed by CNBC Make It. GuineaLoft's Amazon storefront sells hay feeders and no-drip water bottles for guinea pigs, but also acrylic cages and accessories for hamsters, rabbits and birds. While Lin considers herself to be a "veteran guinea pig owner," she's had to gain experience designing cages and products for the smaller pets. 'I'm kind of just the guinea pig girl'Outside of BizWorld, Lin's friend circle is void of other entrepreneurs: "To them, I'm kind of just the guinea pig girl," she says.

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Persons: Bella Lin, Lin, GuineaLoft, Kevin Heinz Lin, isn't, TLeggings, …, Kevin Heinz, she's Organizations: CNBC, The University of Chicago Locations: Sunnyvale , California, Hangzhou, China