THS,
Duck Hunting is very fun IMHO. You don't need a dog if you go to a guided duck camp. Great fun if you get a group of guys up to go. Great food, and all evening to drink and tell lies. Hunts are not outrageously priced depending on the level of comfort and amenities you require.
Although Ark. is known as the duck hunting capital, Louisiana is a close second, if it hasn't surpassed Ark. My bud is there now duck hunting. I've been to Ark. duck hunting once, and always said if I could afford to do it a few times a year, I'd give up deer hunting. It was that fun to me. Couple of ways to do it too. You can do it in flooded timber, or in a blind beside water/river on a flyway. Also, I know there's some duck hunting in N. AL along the TN River, but have never looked in to that.
As GH said, you can get a serviceable shotgun for a few hundred bucks, or you can spend big bucks on a very specialized duck gun, but IMHO, there's no need. JMO, Id get a semi-auto, and a 12ga that handles 3" shells...which I think they all do now these days. Remington is never a bad choice in shotguns or rifles. And you have to hunt ducks with steel shot only.
IIRC you're in or near the B'ham area, and I'd suggest a trip to Mark's to ask some questions. Don't let them talk you in to buying all the most expensive of everything. At a minimum you need a gun, thin, light, layers of clothing that you can layer depending on weather, and amount of work/walking to get to your hunting spot, hip or chest waders depending on hunting situation. Get chest waders initially, and you'll always be ready. You need a hunting license for the state you're hunting in, a migratory bird stamp, and a duck stamp. Mark's can tell you all that too.
If you have nothing of the above at this point, the initial cost is going to run a couple to a few grand, depending on how bare bones you go or not. If you happen to know someone that has a place to go locally, you can get by with a lot less assuming you can find someone with a dog to go with. Primary duck you'll see here in the woods are Wood Ducks, and in places like LA and Ark, these are considered trash ducks, but they are very pretty, though not the best eating. When I lived in Helena 15 years ago, I had a little water hole in the woods about 200yds behind my house where I shot woodies. They drop from the sky like a rock, through heavy timber, and are hard as hell to hit.
Good Luck.