Nearly all puppies and adolescent dogs go through some behavior difficulties. At this stage they know the rules, but forget a great deal of the time. Dog obedience school is very valuable and helpful. It is also important to keep rewarding them for positive behaviors. Don't forget, cats love to sun themselves in windows and dogs bark at least once in a while.
Pets require annual veterinary visits, food, litter, pet supplies, etc.
It can be considerably more costly if your pet has an unexpected injury or illness. Puppies may have diarrhea, need a series of vaccinations, may chew almost everything and often cry or whine a great deal. Puppies do not stay the same size for very long. Make sure you know how large the breed will get before you decide to bring it home. Kittens race, climb, cry and are very active.