As far as I'm aware, people occupying rent controlled apartments (in NYC) can opt to be bought out by their landlord. I've heard a number of stories of people using that windfall (generally buyouts are on the order of $10^4-10^5) to improve their general living situation, and I've also heard stories (including someone I knew personally) of people squandering that windfall and ending up living out of their car.

IANAL...

I believe the landlord is bound by the language of the law, not the contract. If the law enabling grandma's rent control were fully repealed, there'd be no rent control-related reason the landlord couldn't raise Grandma's rent to market rent. Basically, Grandma AND the landlord both needed to know what they were getting in to.

Grandma: "I want this apartment."

Landlord: "OK, it's $250/month with rent control. But just so you know, if they ever repeal that law, and market rate is more than the $250/month you're paying, I'm raising you rent."

Grandma: "Understood. If I were the landlord, I'd raise the rent on the grandma renting my apartment, too."

Isn't a sale a lifetime contract?

Apartment rental is explicitly not a sale. We should probably keep talking about the same thing and not keep moving the goalposts to suit our argument.

Isn't an NDA a lifetime contract?

I have never seen (and certainly have never signed) an NDA that covers an indefinite period of time.