New York City Mayor Zohran Mamdani rode his promise to make one of America’s most expensive cities more affordable all the way to City Hall. But for New Yorkers hunting for an apartment, rents have never been higher.The citywide median asking rent reached $4,200 in June, up 5% from a year earlier and the highest recorded by StreetEasy since it began tracking the market in 2010. In Manhattan — the most densely populated NYC borough — the median cost of monthly rent climbed 5.1% to $4,965.At the same time, apartments are becoming harder to find. The number of rentals available across the city fe...