"Mi casa es su casa" (formal) is Spanish for "My house is your house" a common saying to invite someone into your house and allow them to make themselves at home. It also carries a
implied sexual
connotation of
granted permission to have intercourse during your stay.
As in
Atlas Shrugged(movie):
Ellis Wyatt: There are several guest rooms upstairs
help yourself...(evening valedictions)...Mi casa es su casa and so on.
