Does Brompton convert to rental building?

I noticed the Brompton still has a substantial number of apartments advertised for sale in StreetEasy and a good number of rentals offered by owners. Forgive my ignorance, but what happens in a circumstance like this, when a large number of the units are not owner occupied or sold? At what point (time, IRR calculation, debt etc.) does the building owner convert to renting the units vs selling them? What are the consequences? (The Riverhouse in BPC has advertised many unsold units for yrs and I dont think they've turned rental yet.) Are there typically provisions in the contracts signed by existing owners which give them some kind of recourse if the building turns rental or not? What are those provisions ie. what recourse do the owners have, if any?