From CNBC [emphasis added]:
In fact, a crucial decision Elon Musk was forced to make in 2010 when, by his own account, the billionaire was broke, is one of the reasons Musk has been able to cash in on Tesla's rapid share rise this year: Musk held on to shares at the very moment when a sale to raise cash would have made financial sense.
Musk, who had $200 million in cash at one point, invested "his last cent in his businesses" and said in a 2010 divorce proceeding, "About four months ago, I ran out of cash." Musk told the New York Times' DealBook at that time, "I could have either done a rushed private stock sale or borrowed money from friends."
It's a dilemma that many entrepreneurs face, but there is a big difference between the options available to Musk and the options available to most business owners. Musk was able to live on $200,000 a month in loans from billionaire friends — while still flying in a private jet — rather than sell any of his Tesla stake. Though the root of the problem is the same: intangible assets or, in other words, a business owner who is "asset rich" and "cash poor." And it can lead business owners to the most difficult decision of all: having to sell a piece or even all of their company.