Bava Batra 98 - Building Contractor

One who sells a lot to his fellow, or one who accepts a contract from his fellow regarding a lot, to construct for him a wedding house for his son or a widowhood house for his daughter, he must build a house measuring at least four elbows by six - these are the words of Rabbi Akiva. Rabbi Ishmael, however, says, "This is nothing but a cattle barn!"

Incidentally this ruling teaches that it is not proper for a son-in-law to live in the house of his father-in-law. Rather, the father of the groom would usually build a small annex adjoining his own house, where the newly wed couple could live. This accords with the teaching from the book of Ben Sira: "Lighter than bran is the son-in-law who lives in his father-in-law's house. Still lighter is a guest who invites another guest. And lighter yet is one who gives an answer before he has heard the question."

Art: John Constable - A Cottage in a Cornfield