The Mistress is Served (1976)

Directed by Mario Lanfranchi

A bankrupt Italian count commit suicide and one of his creditors takes over his family villa but he allows the widow, the mother, and the three adult sisters to stay on. The creditor is a wealthy businessman, but also basically an uncouth peasant (who fancies himself an opera singer). Still, the dimwitted, sex-crazed sisters try to seduce both him and his shy, virginal son who accompanies him.