A few years ago I wrote an article about a woman in Arles, France – Jeanne Calment – who lived to be 122 years old. This made her the oldest person in the recorded history of the world.

An intriguing aspect of her story is that she owned a nice apartment in town. When she was 90 – in 1965 – she made a deal with a local 47-year-old lawyer.

He would pay her $500 a month as long as she lived and she would leave him her apartment at her death. This was a beneficial arrangement for both parties.

For one thing, Jeanne was all alone. All of her relatives, including her husband (Fernand), her only chi...