Yeah sometimes you will be surprised what you can find at shelters. You could always ask them if they have a purebred first. It would probably be much cheaper getting it there then at a breeder. Then if you go to a breeder you should be seeing if their dogs are all medically checked and healthy, they have certificates (Look up online as some certificates are easy to get and "backyard breeders" can get them) good care in the home, and also if they are breeding more than 3 types of dogs, don't buy from them as it is too hard to find all the bloodline info, health check ups and all that.
What breed of dog were you looking at getting?
15 Gallon NPT
1g no tech bowl in the making