I can’t speak for the billionaire class, but you absolutely can do whatever you want with your portfolio short of withdrawing funds when you take a margin loan

I can’t speak for the billionaire class, but you absolutely can do whatever you want with your portfolio short of withdrawing funds when you take a margin loan out against it. There are other limitations but it’s pretty free rein for normal transactions like buying and selling standard securities. I can sell any security I want in my portfolio account and leave it as cash and/or buy another so long as I don’t borrow above my margin limit. Most folks employed in the tech sector for any length of time can do the same if they so choose. The only real loophole here is the step up basis on death. That needed closing decades ago it’s so obviously fraudulent. I don’t see much of a difference between securing your loan against a bank account, stock portfolio, exotic car collection, or real estate holding. It’s all just loans secured by other relatively liquid assets. If you sold your home you’d have your loan called in just the same as if you sold your stocks and tried to transfer the money out of your portfolio account. That said - I certainly wouldn’t be opposed to an all or nothing here. Anything to reduce real estate being primarily used as a financial asset over a place to live or do business is a good place to start in my book!