You think have a good prospect engaged, but you need more qualification and can't be sure how to get to the bottom of this sticky Q: can they afford my product/service?

Don't go from a bigwig to an earwig in your prospect's eyes in one moment by asking this inappropriate question. Instead, as John Holland counsels in his best-selling book CustomerCentric Selling, choose a smart and safe alternative.

That is, "What numbers did you use to determine the budget?"

If your prospect answers the question honestly, you'll have all the information you need. You may even find out who actually controls the budget. And if the discussion is taking place with a sneaky competitor just trying to poach information from you, this question will stop him in his tracks.