[Pinatubo]

> We live in a building of 60 units where probably at least a third of those are absentee owners. They're rich enough and the cost to maintain is so low that they don't even need or want to rent those units out.

Another possible cause is that being a landlord in San Francisco is incredibly difficult and time consuming. Last year friends of mine rented out their condo to someone that turned out to be a problem tenant. They had to hire a lawyer and pay the tenant off in order to get him to move. Rather than making money as landlords, they lost almost $50,000 on the deal.

The apartment now sits vacant, and they have no plans to rent it out again.