I don't know the meaning of "I could use a good wife" and also this sentence "you couldn't afford one" in this passage:
She: “Well, I took your suits to the laundromat and got them cleaned and pressed. And I got a great present for your secretary’s birthday. Oh, your Mom called, and I told her you were too busy to go out to dinner this week, but I would take her to lunch Friday.”
He [distracted as he looks through the mail]: “Oh, yeah, thanks. . . .”
She [miffed as blood pressure rises]: “I could use a good wife!”
He [startled and angered by her sarcasm, responds in kind]: “You couldn’t afford one!”