A dog provides a great benefit in unconditional love in exchange for the time and effort he takes. But before you grab a puppy to bring home, consider how much love an older dog can give you instead. In most cases an older animal has a stable, tried and true personality. They are usually trained already to behave in accepted ways. And you can tell this upon meeting an older dog, unlike with a puppy. In any case you should be very sure you have the time to devote to a dog, because they will need to be exercised, cared for, cleaned up after, and in general loved.
You should become familiar with the things you will need to take care of a dog. Knowing what to do in case of housebreaking issues, behavioral problems, health matters, and training needs can make the difference between a well behaved health pet and one that people want to avoid. In the case of a busy lifestyle you need to be aware that a puppy or young dog needs to be allowed access to the outdoors or a "puppy pad" for waste elimination every four to five hours. If you cannot provide this then consider an older dog with the ability to hold such things for a longer timespan. If you have the time to come home and be there every four hours and really prefer a puppy, then a puppy pad can give you that little extra assurance that the dog is going where you want them to go instead of in the corner.
Behavioral problems can come from boredom, lack of previous training, abuse, or other factors. If you are unsure about a dog's potential behavior then you should first make sure there are no medical reasons for it. A trip to the vet will help here. Then try to provide your dog with toys to keep them occupied to eliminate boredom as a factor. Providing your dog with the basics of fresh food and water can also help keep them happy and out of trouble.
A dog comes with costs, like vet bills. You should make sure you have time and funds to afford these bills to help keep your canine friend in top shape. You will need to provide monthly heart worm medicines, flea treatments, dental care, and similar things. Your dog will need vaccinations and may develop other medical bills as he gets older. All of these things should be kept in mind when deciding if you should get a dog.
Training is a matter of time. The younger the dog, the more time and effort you will need to make in teaching the proper behavior. A large dog will need to have the entire family use the same methods to train it. This means enrolling everyone in obedience classes to teach the entire family all the same methods. Consistency is the key for training or retraining a dog to act in the fashion that you desire.