I have researched getting a saltwater aquarium in the past, or a reef aquarium actually, however, I have never taken the time and pulled the ball. The main thing that has actually been holding me back is the cost. The number one piece of advice that I have been told time and time again is to make sure you do your research.
If you are interested in getting a saltwater tank, figure out what size aquarium you want, and then research everything you need. There are many people out in the saltwater world who will give you lovely advice.
However, with that being said, saltwater and reef aquariums seem to be one of those things where you can do your research but you will never fully know how to do it properly until your actually doing it yourself. No amount of research will make up for the experience of actually setting up a reef aquarium yourself.