Most rats and mice should not be bred. Though wonderful pets, many have defects of health, temperament, or structure which should not be perpetuated. Rat and mouse breeding is NOT a money-making venture, if done correctly. An unexpected Cesarean may cost several hundred dollars. This would be an impossible amount to recoup even IF the babies lived, and IF you could sell them.
Most breeders consider themselves lucky if they can break even on a litter.
First time breeders have no reputation and no referrals to help them find buyers. Previous promises of I want a rat just like yours evaporate. Remember, the average litter is 8 to 12 kittens, and can be much more. Even if the kiddies are present, they may get a chance to see the birth of a stillborn or watch the doe scream and writhe in pain attempting to deliver a baby which is too large. Some does are not natural mothers and either ignore or savage their litter.