Another older, more obscure film is My Man Godfrey
. Whilst on a scavenger hunt for a high society party game Cornelia Bullock and her sister Irene (Carole Lombarde) find Godfrey (William Powell), a tramp living on the city dump. Godfrey takes a dislike to Cornelia and decides to help Irene win the hunt for a 'forgotten man'. Soon Irene persuades him to work for her family as the butler, without knowing his true identity. And I suppose you can guess who "saves" the whole family ... yes, the tramp turns out to be financial wizard.
The trailer -
A typical clip -