"If you only cleared the house, you'd be quite happy, wouldn't you?" said Herbert, with his hand on his shoulder. "Well, wish for two hundred pounds, then; that'll just do it." (1.55)
Next to food and love, what is the number one thing a family needs? A place to live, right? The Whites, we learn here, have to pay the bank every month or they will lose their home. Notice that it's Herbert bringing this up. Since he's the one working, it's probably up to him to make this monthly payment. Although he seems cheery about it here, it probably causes him a lot of stress.