honestly I would go with something like 12-20 galls if I was gona go "nano" (unless I wanted something like 5galls, cause thats awesome too, I have dont that before)
so maybe a 10 gall even?
are you looking to go reef?
if so...out of just a wild guess im going to say on price
10gall tank-$9.99
20lbs sand- $20
depending on price of LR... (around here it is $7.99 lbs, but I have heard of it being lower, and I buy mine online) so lets say about $70 ish....? (thats usually the biggest expence)
personally on one that small I would just do a HOB or somthing like a ac 30 or somthing....
lighting, roughly $80 ish?
now this is tottaly a guess but I would think that is "about" what it would take to actually get it started (I lied, I forgot the test kit lol, thats about $17 ish)
tottal guess though LOL Ive never done a nano...(well I did a 5gall nano, but I diddnt use LR, and I used an hob filter)