When occupied, the mansion was originally the Stark family manor, until their only son, Tony Stark, inherited their fortune and soon took on the guise of Iron Man. He donated the mansion to the Avengers and had it financed through the charitable Maria Stark Foundation. It was primarily looked after by the Stark family butler, Edwin Jarvis, who not only took care of the mansion but also catered to the needs of the Avengers team. It served as a place to plan and strategize and a home for Avengers members when they needed it.

From Wikipedia