Remember in "The Visa," George says that Kramer's whole life is a fantasy camp because he fell "ass-backwards into money." Leads me to believe he has inherited something. Although, I doubt he got it from his mother. She was only a matron in "The Switch," and she quit that job anyway. She was referred to as a drunken loudmouth in "The Nose Job," and Kramer's various 'recollections' of his childhood don't paint her as a very fortunate, wealthy woman. What about his father?
Pete