I mean if a sufficient number of residents support it, they can forcibly purchase the land or building they're sharing as a cooperative.

Of course, they should pay market rates for it. Think of it as a private application of eminent domain. As far as I'm concerned, the rights of people to live in the homes they technically own without being extorted by a REIT who owns the land those houses sits on trumps property "rights" of REITs.

Worldwide this sort of thing does happen. Example: the UK system of leasehold/freehold.

Guessing GP means “have the option to buy”, regardless if the current owner is selling.