Breeding, and doing it right, is an expensive undertaking. You may have possible vet bills if the puppies require extra attention. If some of the puppies die, or you have a smaller than usual litter, you may not get as much money from the sale of the puppies as you had thought.
Breeders frequently count themselves lucky if they break even.
Some puppies get colic and scream nonstop for days. These are all very real risks that you are undertaking. Much better alternatives include videotapes that are available. If there are local 4-H clubs, those provide alternatives for children. There is no medical reason why a bitch should have puppies before being spayed.