I have a saltwater tank, and all I can say is that they can be a money pit.
The amount you spend is entirely dependent on what you decide to put in it. Getting started is not cheap, especially if you intend to do a reef tank. About all I can suggest is read everything you can. There are as many opinions and possible setups as there are people who keep saltwater tanks.
Aside from the tank itself, proper lighting can be really pricey - but is only really important if you're looking at keeping specific things, like corals, clams and anemones. In a fish only tank, lighting isn't as important, but you will need more filtration.
As for a list of species, there are literally thousands of types of fish, crabs, anemones, corals, shrimp, snails, urchins, etc, etc. You really have to research to find out which ones can co-habitate and what each one eats - some species require a more established tank, because they feed primarily on micro-organisms that grow in a healthy tank. Some fish are aggressive and will eat other fish, some fish will eat invertebrates, some invertebrates will eat fish, many invertebrates will eat corals so you have to pick and choose carefully. It can be a very time consuming process to determine just what to put in your tank. Even when it comes to hermit crabs there are at least a dozen different commonly available species, some of which are more aggressive than others, some are more carnivorous, and some are more detritus or algae feeders.
I have a 75g fish/invertebrate tank, with no corals. I use a Rena Filstar mechanical filter, a protein skimmer, and three powerheads to keep flow up. I don't have a whole lot in it, some crabs, featherdusters, tube anemones, damsels, and a few other fish.