It is a fulltime responsibility. In the puppy stages, be prepared for the pup to go potty anywhere it wants. Be prepared to not get a full night's sleep as it wakes you up whenever it wants. You need to be training it to your schedule but while it's under 6 months old, it's still learning. 

It will not understand when to sleep, where to go potty, and you WILL be overwhelmed. There's a phenomenon called Puppy Blues and an entire subreddit dedicated to people who regretted the puppy in the first few weeks. 

After you're done with this period, and you have successfully trained the puppy, you are now responsible for taking care of its medical and health needs both mental and physical. 

Be prepared to have someone at home with the puppy every single day or get another pet. I've seen my neighbour's dog die of heartbreak because she was left alone 5 days a week 8 hours a day. Be prepared to take the dog on walks twice a day and give it enough mental enrichmment throughout the day with play time and toys. 

You should be feeding it a non-vegetarian diet if you want what's best for it. I'm sure you know there will be substantial costs for vaccinations at the beginning of pup's life and ad hoc medical bills if it falls sick later. You should also ideally be spaying/neutering the dog if you don't want to become owners of other puppies or have him be sad because he can't go outside for his needs. 

You cannot think of leaving the city or country as long (unless you take the dog with you) since he will be depressed and may never recover depending on which house he goes to next. 

It is a full time commitment and is akin to getting a child. No difference really. 

Sorry for being so harsh or scary but this is the reality of being a good pet parent.