We adopted Bucky from the Providence Dog Pound at one year of age. I don't recommend adopting any pet from craigslist. A pet shelter will have the animal checked by a veterinarian and brought up to date on shots. They also screen the animals for agressive tendencies and can make recommendations for compatability with children or other pets.
Town operated dog pounds typically have a smaller adoption fee than ones run by the Humane Society. Bucky's adoption fee was $25 plus another hundred for a certificate for neutering. You can then get any additional tests or innoculations done at your regular Vet.