I dont pay for the spay or neuter of my puppies.
If I would get a Dog back to rehome then I would.
But depending on the dog I would then pass some /most of the cost on to the new owner.
I feel like you MUST charge something
Too many people pick up FREE dogs and do bad things with them
I dont think you'll find very many breeders who will pay for puppies spay and neutering.
Good luck in your search for your new furbaby
