Best option:

When you assume the store, terminate your relationship with the puppy suppliers. Rehome your existing puppies with responsible families and do not charge an exorbitant amount. Give a rebate if they can provide proof of spay/neuter or spay/neuter the puppies yourself and add it into the cost. If you can, do a home visit. If the family isn't willing to allow you into their home, don't give them a pup. Sketch up an adoption questionnaire, agreement, and contract.

Once the existing puppies have been sold, your problem has been solved