“We were all living up here,” said Ms. Gitti, 48, a fashion designer and the owner of Matta NY, a clothing company, referring to the top level of their three-unit brownstone. After the divorce, she continued to live on the top floor. Her ex-husband, Mr. Bologna, 50, the founder and creative director of Mucca Design and muccaTypo, moved to the garden level; the middle unit is rented out. “At first, I didn’t know when it was O.K. to go downstairs,” Ms. Gitti said. “I think we threw some coins down the stairwell as the signal. It worked out fine.”