I don't think you would have to rehome him, lots of people work and leave their dogs at home. Is there any way that you could come home at lunch time? Or, if that's not possible, maybe find a dog walker who could come and walk him and play with him for awhile each day or even every other day. At least you are leaving him in a large area, and he's not crated all day.
Like others have said, they do a lot of sleeping during the day. I am home all day, as I work eves. I have been off work due to illness, so I am home all the time right now. My boys are very playful in the morning after breakfast. They nap on and off all day long. Honestly, I think the only reason they don't nap all day is because I'm home, and they are nosey so they follow me around to see what I'm doing.
And, it is the same here as others have said. It doesn't matter if I'm gone for two minutes or for hours. Their still react the same way....as if I've been gone forever!