starting sw need help

Five gallons is frankly too small to keep a saltwater fish. Some experts could keep one small goby alive in that, but it would require attention to water quality every single day, no exceptions. You could probably keep a couple crabs or one shrimp in there, but not much else. If you get a good lighting setup, you could probably add a small hardy cnidarian like mushroom polyps or button polyps/zoanthids. These are types of anenomes/corals. Almost nothing except creatures habitually caught in tidal pools thrives in very small tanks.

The recommended minimum tank size for a saltwater tank if you aren't experienced with them is 30 gallons. This is because evaporation has a far greater effect on water chemistry in saltwater than freshwater. In a five gallon, one day of evaporation will change the salinity and pH enough to affect a fish, and saltwater fish tend to be far less tolerant of temperature, salinity, or pH shifts than freshwater or brackish fish, because the oceans are so huge that you simply don't get those kinds of shifts.

If you want to get a good feel on the requirements of a saltwater tank, I recommend reading the stickied thread: "Starting a SW tank, Some good advice" at the top of the forum.

I agree with Ben that a 5 gallon is too small for SW fish. You might be able to set up something with a few pounds of live rock and a small crab or shrmip, but it would require a lot of attention.

Start reading here:
http://www.aquariacentral.com/forums/showthread.php?t=11232

Then go on and look for anything you want more info about here:
http://www.wetwebmedia.com/marine/index.htm

The first link will tell you a lot about how to set up a tank. The second is one of the closest things there is to an online encyclopedia of how to keep saltwater fish. The more you read before you start a saltwater tank, the less money you waste and the fewer fish you are likely to lose. Saltwater takes a lot of patience, because as they say, "Only bad things happen fast in a saltwater aquarium."