How to start a walk your dog business?

Hi, i'm 14 years old and my friend and I want to raise some money by starting a walk your dog business. We've already made a flyer to hang up on some bulletin boards in some stores and restaurants by where we live. We just want to make sure we do everything right and we want your advice to make it go pretty well and make people satisfied. like what we were maybe thinking, for a 30 min walk it's $6, and for 1 hour walk it's $10. We were also thinking maybe if we take them on hour walks, we will bring water for the dogs and some biscuits. So any ideas of how to make it go well? thanks we appreciate it!!