It depends on levels of money. At musk levels, it's cheaper to borrow from your shares on margin, spend that, and never repay anything but interest - no financing involved except lending out your own assets. At multi-million illiquid, you're going to go to a bank, show them accounts and historic income, and because you're an actor with bursty income, they'll smooth out the line and decide if the loan you want is above it or below it. He likely had the means for the down payment and the assets for enough monthlies that the bank felt it was de-risked, but you can also do hard-money loans and similar if you have expectations of payment - but they tend to come with heavy duty strings.
Which is to say - for musks, not like you or I, for the illiquid, very much the same process, but with money managers and the like doing the actual bank negotiation.