決まった言い方はなくsugar daddy arrangement, sugar daddy sugar baby relationshipのような表現でいいと思います。
http://www.youtube.com/watch?v=9PriY7ZV1J4 0:24 she made an arrangement that, she says, changed her life.
http://www.youtube.com/watch?v=Mr9k6gY9vGg 0:11 sugar mommyという言葉もあります。
http://www.youtube.com/watch?v=EkUoSzWS7cM&feature=related 2:57 sugar daddy sugar baby relationship
