Of the 48.2 million rental housing units, nearly 49% are located in rental properties of one to four units, according to the latest Rental Housing Finance Survey  (RHFS) data released by the U.S. Department of Housing and Urban Development (HUD) and the U.S. Census Bureau. For these small rental properties, nearly 73% (14.1 million) are owned by individual investors and more than one-third (7.9 million) have a mortgage or similar debt
"Since 2012, the Rental Housing Finance Survey has been America's premier source of data on rental housing finance and financial health," said Seth Appleton, HUD's Assistant Secretary for Policy Development and Research. "The new 2018 Rental Housing Finance Survey data will help the administration better understand the potential impacts of COVID-19 on the financial health of America’s rental property owners.”
The Rental Housing Finance Survey is funded by HUD and data is collected every three years by the Census Bureau. RHFS is the most comprehensive survey of rental housing properties in the United States, covering topics such as property configuration, ownership and management, rental income and expenses, financing, and capital improvements and expenses. The new release includes summary tables  for areas across the nation.
About 86% of all rental properties contain only one rental unit and 97% of all rental properties have only one building. About 36% of all rental units are in properties with one rental unit, while about 30% of rental units are in properties with 150 or more rental units.
About 72% of rental properties, representing 41% of all rental units, are owned by individual investors and 16% of rental properties with 37% of units are owned by limited liability corporations or partnerships. For properties with 150 or more units, 63 percent are owned by limited liability corporations or partnerships.
About 22% of small rental properties (1-4 units) are managed professionally while 94% of properties with 150 or more units are managed professionally.