Here are 9 ways to see if that sweet puppy is from a puppy mill. Puppies Are Unclean or Unhealthy. The first sign that your dream puppy is from a mill is how clean it may be. ... Puppies Aren't Vaccinated. ... Puppy Mill Owners Won't Meet You At Home. ... Pet Store Puppies are Usually from Mills. ... Puppies are Too Young to Leave Mother.