There are some very old houses behind St. Liborius on Monroe Street in between 18th Street and N. Florissant Avenue, and some of them are still occupied.
Update: The house in the picture below on the far right has suffered a partial collapse of the exterior wall facing N. Florissant in November of 2018.
But others, sadly, are not, and they could be such great houses, only five minutes from downtown. I’ve photographed the houses below before, back in 2014.