I agree, I think an adult dog would suit you best. An older dog should already be houstrained and may be used to being left alone during the day, and may already be good on a leash. You'll also be able to tell right away if the dog has any dominance issues or dog aggression. I agree that a GSD would not suit you --- they have TERRIBLE seperation anxiety. Goldens, collies, and shelties may fit you (if the dog can get some offleash exercise).

How do you feel about shedding? Barking? Drooling? How much grooming are you willing to deal with?