The loans have different risk characteristics than his equity stake, he balances risk by deciding how much of his own money to put in vs. how much borrowed mone

The loans have different risk characteristics than his equity stake, he balances risk by deciding how much of his own money to put in vs. how much borrowed money to put in. (There is no doubt a ceiling — how much of his own money he is able to put in — but there's no reason to assume he wouldn't invest less than that ceiling.) If you have enough cash to buy a house, you might sensibly still take out a mortgage, and you'll need to decide how much cash to put down as a deposit vs. how much to borrow. (The bank will likely set a lower limit for the amount of cash, but you might choose to put down more.) Someone could ask you "why did you choose that number", and you'd give a similar answer.