Playing Parents (1978)

Original title: Jugando a papás

Leonor and Juan are a united couple of good standing that cannot have children. They want to adopt one but do not succeed because he is too old. Leonor proposes Juan an audacious plan: having a child with another woman, offering her a significant amount of money if she renunciates to the child. As it is very difficult to find the girl, they publish an advertisement in the press. Ana finally applies, as she has no job and lives far away from his family, so she accepts the deal.