It is great that you are in a position now that you can explore fly fishing in the salt. I personally think that it is harder to start out in saltwater than freshwater. In a lot of situations you have to cast further and there is always the wind to contend with. It can be hard trying to learn to cast and face the wind day in and day out. Not that there won't be calm periods it is just that the wind blows every time it sees a fly rod, or so it seems.
Salt gear is more expensive for rods and reels. Then a boat or kayak to help getting to the best waters or fish the flats that can't be waded. You can do this though and I don't want to discourage you. Here are some suggestions that will make your learning a little easier.
1. Find a shop that specializes in salt water fly fishing. Make friends with those who work there and the shop can be a treasure trove of information. They know what runs when and where to catch them.
2. Learn the knots used in saltwater fly fishing.
3. Buy the best reel you can afford with a sealed drag.
4. Ask question on this forum one subject at a time so you get the best information about that subject. Broad questions get broad answers.
5. Buy rods based on the particular fish you are after the most. A Trout rod won't work for Tarpon and so forth.
6. Find a FFF Certified Fly Casting instructor and take a few lessons. If you can't find one then a fly fishing guide can help.
7. Hire a fly fishing guide and let him know you are new and want as much instruction as you can get. Even if that means less fish in the boat.