OP I think it's good you came on here to ask for opinions. I think it would be tricky in your situation.
DH and I both work FT but I WFH full time for the first two months and DH also took some time off. We used the time to crate train the puppy, toilet train, get it used to being alone for short periods etc. Thereafter, I changed to WFH 4 days a week for the next 14 months. My job is pretty flexible so I had plenty of opportunity to exercise the dog and keep her stimulated mentally as well. The day I didn't WFH, DH takes her to work with him. She isn't the only dog that goes to work either as others bring their dogs too.
I'll soon be reducing to WFH only 3 days a week so we'll use a dog walker for two hour walks. We've already had some trial walks so the dog is used to it. However, she's going to be 16 months at this point. My oldest will also be home from school early so the dog will have company from 4pm. We already know she's fine to be left for 3 hours.
One option you could consider is finding someone who will look after your puppy for the 3 days you're in. Usually, someone who will mostly chill with your dog at home as, depending on the breed, they can't be walked too much to protect their joints. Then when the dog is old enough, you could transition to a dog walker who pops in at lunch time for a walk.
It can be done with thoughtful planning though you do need to build in the expense.
The other things to consider as pointed out by others: insurance costs, vet bills, boarding costs (we only holidayed in the UK for the first year so the dog could come with us as boarding costs increased dramatically where we are to the point of not being affordable), costs of food, treats and toys. Sontaneous days out will disappear. Everything we do revolves around our dog and is planned around her. It's a huge commitment. Then the time spent on training and the dog walks in the rain and mud. If WFH, you'll need to build in extra time during the winter to account for getting rid of mud/drying the dog etc (depends where you walk the dog).
There's also the increase in mental load. We have a cat who I have never worried about as it's so independent. She didn't care who came to feed her as long as she was fed. In contrast, I find my dog is more akin to my child. It isn't as simple, e.g., as finding any dog walker or dog boarding. And I won't let just anyone take our dog for a walk so Borrow My Doggy (whilst it sounds ideal to help) wasn't something I wanted to do in the end (though I'm sure it works for many).