How's business?
An inquiry into the state of one's business or job. A: "Hi Murray, how's business?" B: "Oh, it's great—we just shipped out our biggest order ever!"
How's business?
Inf. a question asked in a conversation about the state of someone's business or job. Tom: Hello, Sally. How's business? Sally: Okay, I suppose. Bob: Good to see you, Fred. Fred: Hello, Bob. How's business? Bob: Just okay.