Economists worry that Chinese companies are borrowing too much money outside the scrutiny of regulators and planting too many potential debt bombs in the corners of China’s financial system. On May 24, Moody’s Investors Service lowered its China rating, citing the country’s mounting corporate debt.

China is taking steps to address the issue. President Xi Jinping told top ministers in April to stabilize the country’s financial system. Still, solving the debt problem could require drastic action.

“The problems are real, but manageable,” said Arthur R. Kroeber, the head of research at Gavekal Dragonomics, an economic research firm based in Beijing. “The government needs to start managing them.”

LeEco, a catchall name for a variety of businesses controlled by the internet tycoon Jia Yueting, poses little threat by itself to China’s financial system. But a review of the company’s finances shows the extent of the opaque ways Chinese firms can use to raise money — and how failures could ripple through the system.

A spokeswoman said LeEco’s efforts to raise money complied with the law. Mr. Jia declined requests for an interview.

LeEco began as an online video-streaming company sometimes called the Netflix of China. Today, its many affiliates sell smartphones and TVs, buy up sports programming, peddle financial products and back the Faraday Future electric car business, which is based in Los Angeles and employs 1,400 people.

To borrow more than $2.1 billion since the start of last year, LeEco affiliates have turned to China’s vast but poorly understood informal financial system.

LeEco raised $215 million from selling so-called wealth management products online, according to public data. In China, such investments promise a good rate of return and the illusion of a guarantee, but they offer little disclosure. LeEco listed the products on its app as “low risk.”

Mr. Li, the music teacher, bought LeEco wealth management products that promised an annualized return of up to 7 percent. He is not concerned about getting his money back.

“I’m not too interested in where the money is going,” he said. “I have a Le TV and a Le phone. I’m not worried.”