how to start a lawn care company?

Me and my friend wanna start a lawn mowing company together, we are both 14 and want to know the best approach at going at it. What we were thinking is to post fliers all over our neighborhood, and charge 20$ a lawn as a flat rate. If it is a large lawn should we charge more or should we charge by the hour or wat? Also, is all you need a lawn mower, gas, and a little practice?(Neither of us have any practice at mowing lawns) If there is any suggestions they would be greatly appreciated.