One of the kindest things any person can do is to adopt an animal from a shelter or humane society. These are animals that desperately need a home and human beings to love and care for them. However, if you have decided to adopt a dog from a rescue situation, you must go in with your eyes wide open.
For the health and wellbeing of your dog, training should really not ever be considered an option when owning a dog. Well trained dogs are more likely to be behaved and listen, be void of behavioral issues, be good in public, and are less likely to bite. Owners also have a much closer connection with the dog when the time is taken to form a relationship through training.
So you have made the decision to get a dog. Perhaps you had a bad experience once before with a dog who you thought was cute or friendly, but then when you got him home he turned out to be a holy terror, and the whole thing turned into a nightmare. Even if you have never had such a bad experience, the fact remains that choosing a pet is a life-changing decision, and it is one that takes a lot of thought and research.