Single rooms, and from the very short description, apparently no running water?

> Each room will have a bed, a desk and chair, heating and air conditioning, a window, and most importantly a door that locks.

This is a very special purpose shelter apparently. It's not something I've ever heard of before, but seems to be simply a building full of what most middle class homeowners might describe as "walk-in closets" -- big enough for someone who is otherwise homeless to crash in for the night.

And as you say, by bypassing basically every possible regulation that might have applied to a typical "residence", the baseline construction cost of these 31 "walk-in closets" is indeed fairly low.