As long as you can keep the attic cool enough it'd be fine. All about ventilation/air movement/temps (that's no matter where you grow though).
With that said, if you're only growing one plant, surely you can find a more stable environment than the attic?
What strain do you think you're gonna grow? How long do you plan on vegging it? I've seen a lot of people on here have success with rubber maid grows. Fairly cheap to set up, too, from what I can gather anyways.
EDIT: With attics you don't only have to worry about heat, but sometimes cold too as they tend not to be insulated as well as the main house, if at all. So a cold climate isn't exactly your friend with an attic grow, more friendly than a hot climate though I suppose.