Mr. Musk is departing from the traditional private equity playbook by putting up far more of his own money than is usual in such a deal, about three quarters of the price. But he’s also following more standard practice for what Wall Street calls a leveraged buyout, borrowing $13 billion that would be transferred onto Twitter’s books.

In other words, his plan for Twitter includes both more cash than the typical buyout and more debt than Twitter may be able to handle, given its patchy profitability.

The structure of the deal means Mr. Musk’s push for unfettered “free speech” on Twitter could find itself in conflict with the company’s basic need to pay off its new debt. If less restrictive moderation of content on the platform leads to more unfiltered exchanges and misinformation, Twitter’s main source of revenue — advertising — could suffer, since most advertisers are wary of associating their brands with polarizing content. And the company doesn’t yet have other meaningful sources of revenue, although it has experimented with subscriptions. If advertising revenue falls, Twitter, which employs more than 7,000 people, could struggle to make interest payments.