Well you can search on the internet for local breeders. They usly have the cheepest rates. thats how i got my dog. But if not search at local shelters. If no luck search pet stores. Last look at fliers. Like at your local supermarkets like publix. thats where i found our local breeder.
Local animal shelter's would probably be your best bet to get a cheap dog. petfinder.com is a good place to start because you can sort out specific breeds in areas. I got a dog from a shelter who was already fixed and had his rabies shot for $13.25. No one wanted him and he was on the urgent list, but he's the most well behaved dog I've ever owned.