Perhaps a google map with your approximate commute would be helpful? I commute 8.7 miles each way in about 40 minutes. I wish it were longer. My only hills are two overpasses and one underpass. You may have to work your way up to that mileage. When I started commuting (and riding after 8 years off the bike) I struggled. I started out with twice a week, then every other day until my fitness improved. This may take several months depending on your starting point (age, fitness, ride, etc). You should try doing the ride on a weekend and see how long it takes and see how you feel once you have ridden that far.