There does become a point where the rent gets so low that the cost of repairs after a renter is higher than the rental income. Even then though vacant houses are a blight and make everything around them worse. Additionally they still use up city resources like roads water pipes and electrical lines so forcing houses to be occupied should really be a priority. If an owner cannot afford to demolish a blighted house then she should be forced to sell the houses so that someone who can will. If that means that the house is worth $1 then that's what it's worth. There should be zero incentive to hold houses vacant for speculative reasons. If people want to own investment properties to rent out that's great there is a need for that and everyone benefits but staking claim to a plot of land in the city and not using it should be strongly discouraged and those people should be encouraged to sell to someone that will use the property.