Most breeders keep their puppies until they are at least 10 weeks old and some longer if they are tiny. I didn't even advertise mine until they were 10 weeks and didn't let them go until they were 12 or more.   
I had my boys neutered before going to their new homes too...except for one and I trust the girl he went to. Are you planning to hold registration papers until proof of spay/neuter is given?     |