Dogs can suffer from a whole host of diseases and other serious health problems. Some of these conditions are inherited, while others are caused by viruses; still others are related to lifestyle and environmental influences.
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.
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.