The Millionairess (1960)

Millionairess Epifania Parerga (Sophia Loren) has everything she could ever want, except love. So when she meets brilliant Dr. Kabir (Peter Sellers), she decides to add him to her list of possessions. Unfortunately, Kabir is not so easily won and presents her with an unusual prenuptial condition: she must live on only 35 shillings a day for 90 days if she wishes to marry him. Epifania accepts and presents a counter-challenge: Kabir must triple a small investment within the same 90-day period.