Golf Balls

My ten year old nephew was excitedly telling that he has now a saving account in a local bank. He is making money with just labor as his capital. With some friends, they have discovered that many used golf balls are scattered around the area where they are playing because of the nearby golf course. What they do is find for golf balls then sell them back to the people who plays golf at the golf course. Now I am thinking, I can buy the balls from the kids at a higher price then resell it to my friends who play golf at a higher price as well.