We got a dog 3 years ago when DS was 15 after years of him asking. To be fair to DS, whilst he was at school and college he walked ddog 3 times a day, before and after school and in the evening. He is now 18 and working full time with a girl friend and busy social life. He just doesn't have the time to give to ddog as before and as I work part time I pick up the slack.
DS says when he moves out he will take ddog with him, realistically I don't think it will be practical for him to do so.
I think I always knew when it came down to it that I would end up being 'doggy mommy' which is why I vetoed most of DH's dog choices as I knew most of the care would come down to me.
We don't have to pay for daily dog care as I work PT and DH is shifts, but you do need to think of the rest of your lifestyle, not just working, e.g. Do you take your DDs to activities? Would they be able to go independently whilst you stay at home with ddog?
He has also cost us a lot more than we initially budgeted for. Luckily we can afford it, and a lot if the cost is 'choice ' e.g. Buying the expensive dog food, treats and toys. You do need the necessities, insurance and medical care (not cheap) but there are things you could pay less for if you wanted.
We researched a breed which was quite 'hardy' so we weren't setting ourselves up for the medical bills if a dog with more common health problems and also have a small dog so he doesn't eat as much as a large one. Also short hair dog so no groomers fees.