I have to disagree. You will be violating the copyright by creating your own image of someone else's print. You are copying his work! If you were just painting the paint-by-the-numbers, which was presumably authorized by the copyright holder, you would not be violating copyright.
Now, will you be "caught"? Made to compensate? Probably not. But it is still copying, and that is what copyright protects against. The issue of whether it's for personal use or for profit does not change the fact that you are making an unauthorized copy of someone else's original work.