Dickie, very nice job, OK, great pic, your some lucky to have it...pretty cool GH and grow room
You will have to decide on where you wanna vent the exhaust, how high up, what wall , etc. It should be a 6" hole to accept your fan/filter set up. I'm excited after seeing this pic. We/you can make this very cool, sleek, stealthy, and highly productive. Start thinking about noise and security OK, There are many things to do , but it will be fun. Is that (sliding?) door the only way in?
There are a few different layouts you could have inside, you decide. I suggest making a 'horseshoe' walk around with the plants in the middle all the way to the back...know what i mean? That way you will have great access , all around , both sides and one end. I would grow 4-6 plants , under two larger lights. With a set up like that you could (as long as the enviro is proper)harvest close to 2 lbs , maybe a lil more , each crop. I would highly advise getting Doc Bud's 'kit' . Yesterday...
Cheers Dickie