setting up a nano could be done to a budget... but as reef has said, it'll be really hard to keep parameters within spec. it has been done before, but only rare cases have been successful.
my advice would be to research everything you would like in it, then start collecting all the running gear now for a massive tank ie. the best skimmer you can get (don't skimp on this one, get one that is rated for a much larger tank), lighting, auto-topoff (not a necessity but highly recommended), powerheads, RODI filter for ASW or a storage container and collection containers for NSW etc.
When you have all the gear it would make a tank upgrade so much easier as if you have gone all out on the gear, most of it can be moved to the new tank.
If you really want to do this nano however, look at getting a decent sized sump tank set-up. it will add to water capacity and make it easier to keep parameters. you will be restricted to what you can keep in it tho, so do alot of research on the inhabitants, and then research a whole lot more.
sounds like alot of work but welcome to marines. :lol: