Mr. Musk is the richest person in the world, with a net worth pegged at well north of $200 billion. But his wealth is mostly tied up in Tesla stock. As chief executive of Tesla and one of its largest shareholders, Mr. Musk owned about a fifth of the electric carmaker as of December. But Tesla limits its executives to using no more than 25 percent of their stock as collateral for borrowing, and Mr. Musk already has pledged a portion of his Tesla shares for other loans, according to company filings.

He could theoretically pledge the rest of his eligible Tesla shares to raise enough funding to buy Twitter. But Tesla remains a wildly volatile stock, trading between $766 and $1,145 in a matter of weeks — which would give pause to banks considering lending to Mr. Musk against his Tesla holdings.

Mr. Musk could also go to banks to help provide the $15 billion to 20 billion in debt financing that analysts say the bid requires, which would be added to Twitter’s balance sheet. But Morgan Stanley, the investment bank that is advising Mr. Musk, is not known on Wall Street for pulling together the kind of large-scale financing a purchase of Twitter would require.