900$/mo isn't necessarily below market rate. I lived by central park in manhattan for $1000/month, and I slept on the loft above my clotheshangers because it was basically a closet.
This is for sure below market...it’s been rent controlled for almost 10 years. Huge room in central Lower Haight. That place should go for at least $5500 between 3 people in a 3 bed/2ba.