Ask breeders at dog shows and look them up in breed books for further information.
Dogs are social creatures.
They will not be happy left out in the back yard alone. You must be committed to spending several hours a day with it. A terrier for example requires a lot of exercise. Conversely, many Mastiffs are content tojust lie on the floor and do nothing at all while you are gone. Even if you get a dog from the shelter or otherwise inexpensively, you will have to buy food, pay for veterinary checkups, vaccinations and routine medical care over the lifetime of the dog.