Greenfield Puppies has been in business for more than 10 years, and is a legitimate way to buy a puppy online. They run extensive checks on the breeders in their registry and require a health guarantee for all puppies. The research and home checks done by Greenfield Puppies prevent puppy mills from being able to list their dogs on the site. They also require vaccinations, records, and a breeder profile for their breeders. Check out their website for more information on their standards and guarantees.