You don't have to repay the loan (for a very loooong time). Let's say you have 10 million in stock. A typical margin account allows you to borrow up to, say,

You don't have to repay the loan (for a very loooong time). Let's say you have 10 million in stock. A typical margin account allows you to borrow up to, say, 40% of that. That's 4 million dollars. Let's say you borrow $1 million and spend it. Currently interest rate on a margin loan is under %2. So every year the amount you need to repay grows by $20k (2% of $1 million, for simplicity I don't count compounding). So in 10 years that would be $1.2 million to repay. But you're authorized for $4 million. If in those 10 years the value of stock doubles to $20 million, then you're authorized to borrow $8 million - the amount you can borrow grows faster than the amount you need to repay. To be clear: eventually you have to repay it but in the corner case it could be done when you die. There are of course caveats. If interest rate increases dramatically, then the amount to repay will grow much faster etc. but you can see how e.g. if you have $10 million then you could borrow and spend $100k to live a good life and never have to sell your stock to fund your life (especially if stocks keep going up faster than interest rate, inflation and your spending habits)