First off :welcome to nanotank!
Startup costs for nanos are noramlly lower but be aware that you will have to do water changes more often since there is less water involved. Most of the all in ones like nanocubes, bio cubes, and aquapods need some type of upgrading to keep a nice reef. Upgrade the pump (maxi jet 1200s are normally pretty good), upgrade the lighting, and remove all the media from the back except maybe one sponge. If you keep one sponge in then change it out every couple of days with one of the other sponges to keep them clean.
OR.... build your own nano! Either way works well. There are a lot o beautiful tanks in the nano section.
Setup is relatively easy, but it is COMPLETELY different than fresh water. Oh and just in case, for top off water use fresh RO/DI water, not more salt water.
Gobies are nice fish choices.
www.liveaquaria.com has a nanofish setion to get you started looking at fish that do well in smaller tanks. Just keep in mind there are more sites out there.
Last thing I swear :langle I moved this to the beginner area to help us keep tabs.