"Two can live cheaper than one
The observation has an ageless, proverbial ring, but the earliest example of it in the Oxford Dictionary of American Proverbs is relatively recent, coming from Ring Lardner's Big Town (1921)."
- Unwritten Laws: The Unofficial Rules of Life as Handed Down by Murphy and Other Sages. by Hugh Rawson.
This is a cool book that explains the origin of some of the terms and life's rules we have all heard time and time again. It's a really interesting read.