The best investment you could make at this time would be installing a moisture/air barrier like Tyvek and some R-19 insulation in the walls, I'd also draft stop every hole and crack you can find with expandable foam. I guarantee it will pay dividends in the future.Set it up......
I have:
4- 600w 6" cooled hoods w/MH and HPS diggy.
1- 1000w 6" cooled hood " ".
1- 6" 420cfm inline fan.
1- 6" 240cfm booster fan.
CD/DWC system
And all the miss stuff, plus cash..........
Talk to me; build it!