Slumlord
The term slumlord is a slang term for a landlord who attempts to maximize profit by doing the opposite of what traditional landlords would do.
Generally, a landlord would maintain his/her/its property in a well-maintained manner, in order to increase profits and attract quality tenants, as such a property will (when the landlord finally does sell) attract a premium price.
Conversely, a slumlord will spend little or nothing on maintenance (generally only the bare minimum required by law for habitability purposes). They will also exploit tenants who have problems getting housing (such as minorities, or people who can't pass criminal background checks) as they can intimidate them due to their limited options elsewhere. Generally they will deal strictly in cash to avoid paying income tax, and often will accrue numerous back amounts owed in fines and property taxes, knowing that it will often take a municipality years (if it ever does) to seize the property and sell it at auction to collect the back amounts owed, and in the interim hopes that gentrification will make the property valuable to another buyer who would likely demolish the property. As such, a slumlord would not participate in a government housing program such as Section 8 due to the requirements to report income and maintain the property in a safe manner.