This really depends on the details of the market. Much of the housing stock in NYC are Co-ops that require the owner to use the apartment as their primary resi

This really depends on the details of the market. Much of the housing stock in NYC are Co-ops that require the owner to use the apartment as their primary residence. (My building is 100% owner-occupied, though we do allow subletting for a couple years.) You can compare prices in these buildings to restrictionless condos and see how much effect investors have. It is noticeable, but not earth-shattering. Many people that live in co-ops probably could have bought a condo if it's what they wanted.