Slap does not charge users anything to set up and distribute challenges on Slap.  Of course, if you want to give people financial rewards such as gift cards or Slap Points, you need pay for those rewards with a credit card.  You can also give winners of challenges low-cost or no-cost rewards like a shout-out on social media, a home-cooked dinner, or a book you’ve written (these are called “other rewards” in the challenge creation form).  The rewards you can offer are only limited by your imagination.