A rich man is either a scoundrel or the heir of a scoundrel.

[Dives aut iniquus est, aut iniqui haeres.]

Proverbs, Sayings, and Adages

Latin proverb

This one has many variants in English, including:

• "A rich man is dishonest himself, or at least he succeeds a dishonest predecessor."
  [tr. Donne, Sermon 140 (1620-04-02)]
• "Every rich man is either an oppressor himself, or the heir of one."
  [tr. Manton (c. 1660)]
• "A rich man is either a crook or a crook's heir."
• "A rich man is either a knave, or the heir of a knave."
• "A rich man is an unjust man, or the heir of one."

It was frequently quoted by St. Jerome. See Laudator Temporis Acti: Mma Potokwane and Saint Jerome for more discussion.