NYC Mayor Zohran Mamdani has an ambitious list of affordability proposals. Michael M. Santiago/Getty Images NYC Mayor Zohran Mamdani has proposed free buses, a rent freeze, and universal childcare to lower costs. Mamdani's affordability plans face funding hurdles, since any new taxes must come from the state. Aspects of his affordability plans have played out elsewhere, showing the nuances of bringing down costs. New York City Mayor Zohran Mamdani's central promise has been to bring down his city's cost of living . But New York's affordability problems are a result of its own success: Despite slowing population growth , the city's housing stock and services are still in high demand, pushing prices up. Cities typically get cheaper when people don't want to live in them anymore — think of Detroit, after its downfall — and not when they're in high demand and growing. So the question becomes not whether Mamdani can make New York broadly affordable for everyone.…