Another is that, should the need arise, stock can be sold at the drop of a hat. It is liquid and fungible so a stock-collateralized loan is seen by banks to be a very safe investment. Houses are not.
In this case explicitly I suspect it has more to do with the uncertainty of the deal going through AND not wanting to incur the tax penalty ALONG with the share penalty (liquidating $30 billion in TSLA would affect its price for sure). If you sold the shares to raise the cash, paid the tax, and then the deal didn't go through and bought the shares back, you'd be out the tax (with a stepped-up cost basis to be sure).
I'm not following the whole lifecycle. You borrow against your stock, spend that money, and then repay the loan using stock? Without having technically sold the stock?
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)
I guess the risk here would be that the stock goes to 0, you get margin called AND you are now on the hook to pay taxes.
I know Ken Lay did that exact chain of events a lot to cash money out of Enron before it's bankruptcy.
Most of the ultra-wealthy live on debt. Here's the basic scheme:
- Let's say I own $10B in startup.com stock, but haven't sold it. My income tax burden is $0.
- If I sell the stock, and taxes are 40% in my country, I get $6B, and the government gets $4B.
- If I keep the stock, and borrow against it, I pay no taxes, but I do pay finance fees (e.g. interest). The finance fees work out to less than taxes.
The trick is to never realize gains or income. Debt lets you do that.
One more trick is that a lot of purchases are "investments." If I buy a mansion, yacht, and Picasso on debt I can use them. When I'm bored of them, I sell them, and pay off that debt. I've probably made money on the mansion and Picasso, and lost money on the yacht.
I've paid a little bit of interest and a little bit of tax, but much less than I would have otherwise.