Well I leave my window open all day, and my closet doesnt close all the way - its left open about a centimetre, so thats enough ventilation. Plant growth doesnt seem to be stunted in any way either.
You dont really need the long tube florescents (the kind youll see in a fish tank) you just need a few 'energy saver' bulbs, which are the spiral kind. Fit a few E40 fittings in there to screw the bulbs in, and when your plant starts budding, add the CFL's for sidelighting, which will make the buds a little bigger and more compact aswell - oh, and more potent.