Negative things that dogs do:
1-Chewing everything in sight due to boredom and lack of exercise.
2-Defecating and Urinating all over the house
3-Barking, Wining, Crying, all night long
4-Destroying the house from lack of exercise and mental stimulation (for example: tearing apart the couch, ripping the door of the hinges)
5-Becoming dog or people aggressive from lack of training and socialization
6-Becoming pregnant because they haven't been spayed. (in the case of a male, knocking up the neighbors beagle cause he smelt her in heat)
7-A medical complication resulting in a $5000+ vet bill.
8- Allergies, Skin and Fur irritations
9- Gum disease, cavities, bad breath and rotting teeth (which would also result in a large medical bill) from not brushing the dogs teeth.
10- Shedding hair all over the house.
11- The dog could hunt and kill smaller animals (such as birds, cats, squirrels, smaller dogs).
12- The dog might attempt to be the alpha or pack leader and dominate you all the time.This would also result in the dog not listening to you or doing anything you ask.
Etc.....
Dogs are fantastic and I can't wait to have one or two of my own, but they aren't to be taken lightly. They need to be well taken care of and well trained and they need a loving caring owner to provide them with the best home possible.
Hope this helps
Good luck with your new puppy
Blessings