Per Buy, Borrow, Die, they could take a margin loan using that $1M and use borrowed money (say $100K) to pay the rent. With enough accumulated shares, they wouldn't need to sell the shares in their lifetime. After they've passed away, they would pay off the loan and the stock gets a free step up to the appreciated cost basis.

How would you pay off the loan without selling at least the interest?

that's assuming the stock is actually transferable though. that day could never come