There are two types of horses in the GQ books: working horses that pull the Blackwells’ carriages, and recreational horses, most of which see little use. The horses that get the most exercise are Henry’s Marigold and Martin’s Partita.
The Blackwells keep their horses in a stable several blocks from their home, which was the custom at the time–there were whole neighborhoods of stables smelling of horseshit, which rich people understandably wanted at some distance from their grand residences. Henry and Martin walk the few blocks to the stables whenever they want to ride.
Just to give you an idea of how RL rich people housed their horses, this is Cornelius Vanderbilt’s stable, built in 1880. This photo was apparently taken in 1916, after the family had converted the stable to a nightclub (!!!), the era of horse-drawn anything being well past for the likes of the Vanderbilts.
I don’t see Mr. Blackwell wanting anything quite so decorated, actually, but I do imagine the Blackwell stables being fairly grand nonetheless.
But on to the horse visuals :)