To learn more about the CNBC CFO Council, visit cnbccouncils.com/cfo From New York to Vancouver to London, a once-niche policy idea is moving into the mainstream of urban finance: taxing pied-à-terre properties , second homes, vacation apartments, and luxury units that sit partially or entirely unused. New York City is just the latest example, with Mayor Zohran Mamdani and New York State Governor Kathy Hochul supporting the tax as part of a state and city effort to make up a big budget hole .