"Grade" dogs are called mutts. Even so-called purebreds should be assumed to be mutts if not registered because how can you PROVE there isn't a Poodle 5 generations back in your Labrador's pedigree without proof of bloodlines?
When buying a mixed puppy, DON'T get it from a breeder unless it's a sport-bred mix from health tested, proven parents. Breeding should always be done with health and purpose in mind. If you don't know how to tell or can't be bothered, get your mutt from the shelter. Shelter dogs are great (I have two, a mutt and a purebred ex-racing greyhound).
If buying a purebred puppy, ALWAYS insist on papers, and keep looking if the parents aren't health tested AND titled (conformation is a start, I like at least one sport title as well). The only part of this that doesn't apply to sport-bred mutt pups is the papers part.
And don't fall for the "hypoallergenic" marketing with mixes. Most doodlemutts aren't.
"But I just want a pet, I don't need a show dog!" I hear you say. Even the very best breeders WILL produce good pet puppies. In fact your chances of getting a good pet are higher if you choose a good breeder than they are if you choose somebody who bred their dogs because they were cute and "good pets", because many show breeders have extremely high standards for temperament and health, whereas Fluffy's owner who bred to Bingo down the street because they wanted cute puppies has not put so much thought into the litter. If you're lucky you'll get a good puppy from Fluffy and Bingo. If you're not you'll get something with genetic health/temperament problems.
MAKORA THOROUGHBRED SPORTHORSES