Several federal agencies have properties to sell. In fact, HUD sells both single family homes and multifamily properties. Check them out- one might be just what you're looking for!
From HUD
From the Department of Veterans Affairs
From Federal Deposit Insurance Corporation
From Internal Revenue Service
From US Army Corps of Engineers
From Customs
From the U.S. Marshals Service
From the Department of Agriculture Rural Development
From Fannie Mae
From Freddie Mac
From Realtor.com
General Services Administration
Federal Deposit Insurance Corporation