I know you find a need and then fill it. It is also said the best product to sell is one you created yourself. Informational/electronic products being the best. But what if you have found a niche and an idea. How do you find out if it will sell? For instance, I like word search puzzles. My children like word search puzzles. I have an idea for creating word search puzzles with a twist that is different than the normal everyday wordsearch puzzle on paper to be solved with pen or pencil. How would I go about finding out if this "new" product will sell? I plan on creating some and selling them on ebay to test the waters. Any other advice/suggestions?

Thanks,
Ken