Is there no way, to just take a normal residential building, tear everything down inside except for the exterior walls and fill it with japanese sleep coffins? Even if zoning laws would forbid this- life should find a way as they say.
http://www.loopnet.com/california/san-francisco_apartment-bu...
2950 21st Street is 4900 square feet and costs $3M. Right now it's 4 x 1200 square foot apartments, which go for about $45/square foot. Yowzers, that's $4500/month.
Let's say you take each of the two floors and remodel them: two full bathrooms designed for shared tenancy, each coffin takes up 8 feet by 5 feet by 4 feet and you stack them two high, with 8 sqft of hallway and such added in. That's 48 sqft per coffin stack, so with perfect layout you get 100 coffin stacks. But you need room for bathrooms for 80+ people, and that means 8 stalls, 8 sinks, and 8 shower cubicles, taking up about 20% of the space. OK, your max occupancy is 80 where it used to be 16.
The good news: you can charge as little as $250/month. If you spend enough on insulation you won't need to spend much on heat in the winter, but ventilation is going to be a problem.
Nobody gets a parking space.
Lice will be a problem.
Cockroaches will be a problem.
However, the issue that will get you the status of first slumlord to be sentenced to life in prison is fire safety.