I'd check craigslist, I'm sure you could find a small biocube or nanocube setup with live rock and all. Many of people (like myself) underestimate just how much work it takes to maintain a saltwater tank.
Well, if you are only going to get some clown fish or damsels its not too bad, but when you start getting in coral its nuts.
Anyway I'm sure on craigslist you have find someone getting out of saltwater and selling their setup for a about $100-200 depending on how nice the setup is.