Since its only a mile and on the streets any bike will work as long as it is comfortable. A mtn bike wouldnt be worht the money unless you actually do mtn bike. Road bikes can be as expensive as mtn bikes and they arent practical for your reasons. Road bikes have thin tires that may buckle or loose traction through dirt, gravel and such. So i would recommend something cheap and easy, nothing hardcore. Bike manufactures are now making hybrid bikes. Hybrids are sorta road bikes in the sense thats all they can do really. They wont take you through the trails fast, but they will keep good traction on gravel and terrain. thats what i would recommend for you. They might have shocks but they would only be good for looking at, no disc brakes, less gears, thick tires, bigger frame.