"That's the key to business, isn't it? Find a need and fill it. Just a hobby, though, a little way to pass the time in my old age. Keeps me in mead and all." Slughorn lifted a nearby mug in a toast to the sentiment. Brewing was thirsty work, after all.

If that little speech didn't urge his customer to speak about his own business, well, he'd have to be a little less subtle in drawing out the information.