I am not going to say our mad - but it will be a huge commitment time wise and maybe financial.
Time wise because not only does it need walking, but it also needs training - training can happen on walks - and its a perfect time to do training...but training can't only happen on walks. If you have a dog that is used to doing whats it likes and is "naughty" the training is going to be pretty constant. So I guess what I am saying is to start with the training will be quite relentless. Though on the plus side - the training will probably to a certain extent exhaust it, so that may have a knock on effect of improving its behaviour. I know someone who is having trouble with a 7 month adult giant breed puppy - they haven't done any training (despite being told again and again that it was essential) it is all going tits up, - there solution is to commit to 2 hours on the weekend......it doesn't work like that - you need to be consistent, and it is constant. and then once they know what is expected of them and how to behave it eases off......
The financial - because you have very little experience of dogs and you will need to achieve as much as possible in the next 6 months - I would say the best possible thing you could do, to make it successful, is get the support of a reputable trainer and have sessions with them, so that they then offer you support and guidance. Then the other thing is that once you have the baby you may need to at times use someone to walk the dog for you.
So I am not saying don't - something is drawing you to this dog, but if you do, go in with your eyes open. Knowing it is a HUGE commitment required from you.