Instead of taxing the rich, Mayor Zohran Mamdani could fill nearly half of NYC’s projected  $5.4 billion budget gap  by simply collecting unpaid taxes and fines from deadbeats. As of Feb. 28, the city was sitting on $1.1 billion in uncollected property taxes, according to the city Comptroller’s Office. And it has also been unable to collect another $1.3 billion in Environmental Control Board fines usually issued for construction, zoning, and safety code violations, the Finance Department said.