Many breeders are spaying/neutering their very young (7-10 weeks old) puppies before sending them to you. I feel this is unhealthy for the puppy and creates long term health problems. In fact, I feel so strongly about this that altering one of my pups before 6 months of age voids the warranty. Ask YOUR vet.
My puppies are sold INTACT. I do NOT spay/neuter my puppies before you get them. My vet wouldn't if I wanted to as the policy at her clinic is a dog must be 6 months before surgical sterilization. If you are not interested in breeding, you might want to have your puppy altered by your vet at 6 - 18 months of age. There are a few benefits to your dog's health that come with surgical sterilization. Again, ask your vet's opinion.
And do it BEFORE you buy.