not to become a breeder but because I want her to have a litter before she is spayed
If someone allows - by choice or through inaction - a bitch to become pregnant they ARE a breeder.
So you have a to make a choice - do you want to be a RESPONSIBLE breeder (do the health tests to confirm that your bitch is healthy, have her evaluated to confirm that she is breed worthy, study her to find her faults and then study the males to find the one that will compliment her faults but not bring any others, check out potential puppy buyers and be ready to take back ANY of the puppies - at ANY age - if their owners cannot keep them) or an IRRESPONSIBLE breeder (pick any male, throw them together, have puppies and sell them to whomever).
Those are your two choices. If you want to be a RESPONSIBLE breeder then the first steps are to have your bitch tested - health, structure, temperament and working ability.