The transaction is the largest single transfer of dwellings in the city's recent past. : SANFORD – Longtime Sanford and Springvale landlord George Sleeper has sold 108 apartment units in one of the largest transfers of real estate in the city’s recent past. The units, which are located in about 20 properties, have been sold to a company registered in Maine with a New York connection, White Bark Properties LLC. The deal closed Nov. 5.