I adopted my Irish Setter from the Detroit Humane Society when he was two years old. He had basic obedience training, was housebroken, and good with children. It is amazing that we got such a wonderful, healthy setter. I think he was the last intelligent Irish Setter born. I can't imagine why he was given up, they did't tell you back then. Perhaps it was his energy level, which put the Energizer Bunny to shame. You have to realize, that when dogs go through their adolescent phase, they forget their training, act rebellious, and otherwise try the patience of their owners. They are often given up just before they hit the "adult" mark and start behaving. So, a diffecult to handle young dog can be perfect for somebody else simply because of timing.
The Bouvier we took in at age two had no training and never been in a house. It didn't take long for him to learn the basic rules. He had fear issues that we did not understand at the time, but turned out to be a real good dog.Enrolling him in obedience training right away helped a great deal.
The Shiba Inu (?) who landed in our laps had been abused and had various issues. By the time she was adopted, eight months later, she was no longer afraid of men (or markedly less so), walked on leash, sat at the door to be let out, learned sit, stay (short time only), down, her name, playing is fun, riding in the car is fun, and numerous other things. A fine dog, but it took eight months to get her there.
If you get a dog from a shelter, you will be the rescue person. As stated in a post above, you may be getting a dog with no real issues who will be a fine pet for you. If you get from a Rescue organization you will have a clearer idea of the dog's personality and he will be healthy and trained. If you go to a reputable breeder, you may be able to get a real nice dog that somebody returned, which would be like getting him from a rescue organization but with papers. You can often get a real nice, even show or breeding quality, dog from a breeder for far less than a puppy would cost. In any event, follow the advice given to you. If they tell you to crate the dog, for heaven's sake, crate the dog. Enroll in an obedience class. Feed high quality food. Have fun