Making sure you have a sitter anytime you want to leave the house for long periods.
Grass has dead spots all over it from urine.
Picking up dog poop in the yard.
Dog can get sick and can be on expensive meds for the rest of their lives.
Dirt or mud being tracked through the house.
House smelling like dog.
Garbage or food being eaten if you forget to put out of reach.
Expense, (veterinary, feed, emergencies, carpet cleaning when there's an "oops" in the house) dogs can be very expensive especially if you don’t have a good job. Sometimes the responsibility of the animals must take precedence over a job, or interfere with personal plans they are as demanding or needing as a young child.
They require most of your attention
A dog can be a marvelous family pet, a companion, a friend, a protector. However, there might be some disadvantages or should we better say potential down sides to owning a dog. I'm not suggesting it isn't a good idea (far from it) but you might want to consider these.
Dogs need walking for exercise, dogs need 'exercising', especially bigger dogs, without twice daily exercise they will get unhealthy and begin costing you money. Having a large back garden does not count.
That brings me onto the second caution, vets bills are extortionate, although one can get pet insurance nowadays.
Going on holiday is problematic, you either need a dog-sitter or someone to take the dog or you put them in kennels. This is usually fairly expensive and painful for you and the dog. Image doggie prison.
Dogs are very attentive, loving animals, but it's worth considering these three disadvantages before committing to a dog for many, many years.