Even routine veterinary costs can be high for dogs as large as a Newfoundland.
They do not do well if tethered and can scale or push through many fences.

Newfoundlands tend to be good with children and other dogs, but they do not always realize their own size.
Wagging tails can knock over a toddler and playful paws can seriously injure a small dog.

Newfoundlands shed. A lot. Twice a year they shed even more.
They require regular daily exercise and should be fit and muscular. Daily walking of 2-3 miles is typical. “weekend Warriors” are at risk for injury.

Newfoundlands drool. There is no way to genetically select for a dry mouth.

They drool on your clothes, on your walls and on your sofa.

Newfs mature slowly. They are puppies until close to two years old and do not completely finish growing until three.
Even though they are very large they are still babies for a long time.

Newfoundlands require regular grooming: daily and weekly brushing, regular baths and trimming of ears, chest, and feet.
This is for hygiene and health and not just for “looks”.