This is always a subject that will arose a lot of discussion - all I can do is relate my experiences!
We do both work - and when we got Honey we both worked very busy jobs (but my job was primarily shift work). My job has changed, and I think to be honest we would have struggled for the first year had my job not changed. While my work is more during the day, I get home just about every lunchtime - if I can't get home, we do have a friend who will look in on her. We have had one day where this wasn't possible, and she was left for just over 6 hours with no ill effects, but I genuinely feel she wouldn't cope with that on a regular basis. She doesn't need much from her lunchtime visit - if the weather is nice, she likes a potter around in the garden, or often she just sleeps on the sofa, but she does need this extra bit of companionship from us through the day - some days it's only 1/2 hr, others it's nearer 2... However she does need to have a good walk in the morning, and she also gets another one in the evening. Even as a young pup, she was left up to 4 hours now and then, but we were careful to build this up from the day we got her! Today she hates me as I'm off sick, so she's currently sulking in her bed...
You would definately need to get someone to visit one way or another - a dog walker would take the pressure off trying to fit in an evening walk, or if you would prefer, I'm sure they could just visit and play for the session. It may be once the dog was older they are a personality that does cope with long periods left alone (my Dad's Border Collie is left 8-9 hrs since Mum died, but I have witnessed that she really does cope fine with this - if not Dad would have had to have rehomed her - but she is 9 years old!), but I wouldn't rely on this... and it certainly isn't going to happen in the first 18 months, I would imagine.
Working and dog ownership does work, but you have to have some back up - our friend offering his help was the point when our dreams of owning a dog actually became plans, as without this, we couldn't have considered it.
Hope this helps - dog walkers aren't hugely expensive, so hope this may be a solution for you! I really wouldn't recommend giving a pup unsupervised access to your garden, as you may have lots and lots of holes dug!!