This is why using Tesla stock to source cash all the time gets hairy. If Tesla shares fall below a certain level, the banks can call in those personal loans — leaving Musk on the hook. And the quickest way for Tesla’s stock to drop off a cliff is for investors to get wind of a big Musk sale. And of course, he needs to make sure that he still holds on to all the Tesla stock he’s pledged as collateral to the banks. Unfortunately, though, the easiest way for Musk to fill the gaping hole in Twitter’s balance sheet is to sell Tesla shares. You see how this could be a problem.