The main thing that should come into play when deciding where they are is "where is their hunting grounds?"
If they're too far away from the humans they hunt, they're too likely to be spotted traveling. Especially if there's more than like, three of them. If they're too close (like right in the middle) they'd risk being too easily found, and the handler/leader would have difficulty with the ferals trying to break free to hunt on their own (because they prey, it's just so tantalizingly close!).
So, assuming they pick on homeless and squatters in the Barrens, they'd likely also be living in a Squatter situation, maybe in a dark basement of a condemned building, behind a locked door, while the handler walks the streets, looking for the next target. I personally like this idea because it lets you have the runners walk into what will feel like the den of a serial killer. Disturbing, dark (they're all blind, and see astrally, why the fuck would they need light?), smells like blood and feces, and the astral there...
Depending on how the meals are "prepared", it's possible the area may even have a small background count (no higher than 2, most likely 1). Though Street Grimoire implies the Barrens have a background count of 1 just from how violent they are at base, so it may add together. I dunno. Regardless, the astral would probably be full of the mindless hunger that feral ghouls feel when they need to feed.