Novel about men switching places

[arbooklover]

A friend of mine read a novel in the late 60s or early 70s and can't remember the name. The plot is roughy this: two men agree to switch places. The first man is sick and pays the 2nd man to care for his son. The first man sails to Europe with the 2nd man's wife, who will collect the insurance money when her "husband" dies, but on the trip, the wife and sick man fall in love, and he has successful surgery when they reach Europe.