I would check Craiglist for a deal on a used tank. Ive read about some GREAT finds on craigslist. I know theres a fish store around here too that sells used aquariums, so if you have something like that, check them out too. I would get As big as you can find space for in your house. Bigger tanks are more forgiving as far as water param go. I did a 55 for my first SW
tank and now I wish I had done bigger. Bigger allows for more fish, and there are a lot if really cool fish that require bigger tanks.