The least expensive 1-bedroom apartment in Manhattan is about $3000 a month. Nobody who is poor lives here. All fingers point to the landlord hiring off-the-books contractors to renovate his buildings.
Maybe; I would suspect modifying the building to rent out rooms for a lot less than $3,000.
There was a fire a few years back in one of the north Jersey towns overlooking Manhattan (Englewood Cliffs, maybe), and the fatalities included people from various countries living in basement “rooms” (as opposed to a basement apartment) that had been illegally added. Heat and electricity are often added, without permits, inspection, etc.
in the neighborhood.You seem unfamiliar with "RENT CONTROL"