I never claimed horses didn’t exist in Manhattan. But do you think there are really any private homes in Manhattan where people are keeping their own horses?
In my neighborhood in Brooklyn, (Fort Greene)there are many ‘single family’ houses that have been turned into apartments. Their original design was for single family dwelling.
Private horse stabling is still allowed in NYC (M.C. §161.23), and most homes built before World War I (i.e., almost all of the single-family homes in the borough of Manhattan) were built with a horse stable. How many of those stables are still standing is the question.
There are a very few, and they are not all that expensive (by Manhattan standards) because they are at the very tip-top of the island, 12 miles from the Battery. But still in Manhattan… look in the NW corner of Inwood, around W 217th St.