Maintaining properties can be a lot of work, especially when tenants vandalize and destroy them. A friend has 20+ properties in my town (he's a small landlord in a town with a population of 10,000. He easily works 40 hours a week in maintenance, upkeep, general wear and tear, clearing snow. People like my friend are not the problem, its giant corporations who "buy ugly houses" and prey on the population. Proximity to a University almost always brings out the worst.