alex steup lives in a 10x4 1/2 foot closet. >> that was my bedroom for many years. >> reporter: that's her roommate tristan who grew up here. tristan recently enlarged the living area by adding plywood. he's hiv positive. >> i built that out to expand this space because this room could stand to lose a little bit and i needed the money. >> reporter: did he envision yourself at 33 living in a closet. >> i don't like to call it that. >> reporter: what do you call it? >> a second living area. uh-huh. >> reporter: beyond the semantics of it, we have a case of outside appearances sometimes being deceiving. it is old news to sam moss, a devoted advocate for public housing and critic of san francisco's status quo. >> saying the housing situation is a crisis has become a cliche at this point. it is beyond crisis. >> reporter: more like a self-imposed crisis due to the city's zoning restrictions against high density house. now tristan is a victim of that. he rents the closet to alex because he needs the money. why? his father died last april and never transferred the lease. do you see where this