Replying to Getting a dog and working

I've been planning on getting a dog (rescue around a year old, not a puppy) in the near future, but one major concern is what to do with the dog while I'm at work from 6:30-3 monday-friday. however, i live a very active lifestyle outside of that, and was thinking a short walk before i leave in the morning and then tons of hiking/biking/running/etc. in the afternoon would work. basically, what do the other dog owners of ns do?

my roommate is still figuring out his plans, but he might be around for a bit of the summer, so he can probably help out some days, ill try to get (read: bribe) friends to stop by if they don't have to work during that time, or even a dog walker (but that $ will add up fast). but would it be a bad idea to leave a dog alone for 8 hours (with food/water/toys/etc) if i need to?