Why is the Williams's house for sale?

Just rewatched this the other night ~ part of my thanksgiving ritual and wondered that as well. I'm assuming due to husbands work that perhaps they had plans on moving into a bigger home and it just did not get explained (perhaps was edited to save time).

The house was for sale pending her decision for a divorce. She had to play the role of the Mother/wife/cheated one in the face of her Mother-in-law, a woman of traditional family values. Those women don't divorce, they don't cheat and their spouses die a natural death.