The Frisco garage at Aanya and Ishaan Thakur's house is always buzzing. It's the sound of money.
"As you can see, the sound, it's really loud," Ishaan said.
The sound is graphics cards whirring away inside their rigs, mining for cryptocurrency.
"It's just finding random numbers in hopes of finding something valuable," Ishaan said. "It's something that crunches up a lot of numbers, if you want to do it for bitcoin mining."
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Some kids have lemonade stands. The Thakur siblings tried that but wanted to think bigger. They thought about investing in bitcoin, but the price was too high, so they deciding to mine for cryptocurrency instead.
"I just tell them we're just mining in the garage," Aanya said, explaining what she tells her friends about their new venture.
In traditional mining, heavy equipment digs through layers of rock to find coal or precious stones. In cryptocurrency, mining computers do all the digging.
"But instead of getting diamonds, you're getting bitcoins," Ishaan said.
The siblings started a company called Flifer to mine mostly for ethereum, a cryptocurrency similar to bitcoin. They're making more than $30,000 a month, investing some of that into buying more equipment to expand their business.
"So it's been a good investment," Ishaan said.
They've outgrown their garage. They have banks of computers in a data center in Dallas, mining for digital currency. The garage is now their lab and warehouse, filled with pricy, hard-to-find parts that they have to wait outside stores before they open to be able to buy.
"I promise you," Ishaan said. "Outside of this, I am just a 14-year old kid."
The siblings plan to use the money they make to pay for college and graduate studies. Both said they want to be doctors one day.