Who are "the bosses of the buildings?"

The correct answer is:

The landlords.

In the account of the harsh existence that he and his family encountered in the one-room tenements of South Chicago, Richard Wright's "The One-Room Kitchenette" refers to the building landlords as "the bosses of the buildings", who were keeping black people in specific apartments, without any mobility, and developing racially restrictive housing covenants.