An apartment in Battery Park City that former Police Commissioner Bernard B. Kerik secured for his personal use after Sept. 11 was originally donated for the use of weary police and rescue workers who were helping at ground zero, according to a real estate executive who has been briefed about the apartment. After the cleanup had settled into a routine that fall, the executive said, Mr. Kerik, who was still police commissioner, asked to rent the two-bedroom apartment for his own use. During his use of the apartment, Mr. Kerik and Judith Regan engaged in an extramarital affair there, according...