-join this website!!! It's like TCS for fish!
I'm a member there (same username) I have learned soooo much valuable information from these wonderful folks! Read through their forums on fish care/etc and tanks before you even start thinking about buying a fish tank.
It takes a long time to properly cycle a salt water tank - it takes a lot of patience, but it is SOOOO worth it! You can't add your fish all at once eithor- you have to cycle the fish in depending on the type you get. And keep in mind- certain fish are ranked according to aggression/etc....so be careful when selecting. This website could recommend some good combos!
I'm planning to set up a 100 gallon salt water tank within the next few yrs. at our new house (I had an 80 gallon and two 10 gals. at my old house as well as multiple betta tanks/etc - i LOVE fish!) (i say i'm planning to set up a new one in a few years because they're NOT cheap!
Gotta save up!
Whatever you get, keep in mind the more spacious the tank, the more the fish will flourish- invest your largest amount of money in a good quality good sized tank (I would do at LEAST a 60-80+ gal. if you're considering salt water and want a good variety). Also consider what filters and all you will need and how you will need to maintain the water.
Once you get your salt water tank cycled and established- it's really not too much more trouble to maintain than a fresh water. Definitely go for it! Just be sure to do your research first!!!