The Warbucks's Mansion is the home of Oliver Warbucks, Annie. In the musical it's also the home of Grace Farrell and Sandy. In the story Annie goes to a mansion to spend a week with Oliver however ends up there as an offical home because Oliver fell in love with her.
In the book, Oliver likes Annie but despite that, he has a wife that hates her. She wanted to return Annie however caught in the act of disgust by her friend. She kept her however similar to Miss Hannigan in the musical and movies. She hates her, and adopted another orphan named Selby. She likes him more than Annie. End wants him to murder Annie.
In the 2014 film, there's a character named Will Stacks who's a businessman who's also a candidate for mayor of New York now despite that the building inside is very high tech hence being a billionaire.