I completely agree with Cearbhaill about reading a lot. The actual work isn't necessarily a lot more than FW, but the background is a good bit more complex. It's true that you can do things less expensively if you are good at DIY and finding deals, but you have to know what you're doing.
A 30 gallon tank is quite workable. You will be limited to a few smallish fish, but it can be an excellent display.
The first step is to figure out what you want. Are you interested in fish only, or would you like to try and set up a small reef with corals? Many people think they only want fish, then fall in love with invertebrates once they start getting to know them.