Ask HN: REJECTED. Would you be willing to contract-to-hire?

If a potential software engineering candidate has interviewed with you and you found that this person was passionate about what it is that you're doing, but after tossing a couple of puzzles and technical questions at them, and not feeling that they're quite where you need them to be, would you be inclined to offer a contract-to-hire position if they asked (given that you'd enjoy working with this person)?

Do you think this is a decently good idea? Should a candidate ask?

Any big/well-known start-ups or companies willing to do this?