I personally am an advocate of stand alone dwc. Its pretty simple and cheap. Plus it has an added benefit of being able to position your plants any way you want which in a closet grow can help your yield a ton.
You could probably pull off a really sick 2 plant stand alone vertical grow in a closet with 1 400 watt cooltube. I would guess with the right stuff you could pull off 1/2 a lb easy and within a year you could be pulling a 1lb easy from that closet with two plants.
5 gallon painters bucket( home depot 2$)
3" net pot bucket lids( grow store 3$)
air pump and stone(petco where I am at - 12$ for air pump stones and tubing..go with black tubing to beat algae build)
hydroton(10$ for a bag of it)
grow cubes(5$ - 20 grow cubes)
400 watt digi light from amazon(130$)
I run a 1200 watt vertical dwc stand alone in an 8x4 and due to heat issues I also picked up thin ir foam(grow store) for the outside of the buckets to keep the water temp down. If you have money try and get a ppm/temp meter. You will never run into problems of root rot or overnuting.. and I can tell you from experience if you want to grow the right way the first time don't skimp on the necessities.
ph metere - 65$
ppm/temp - 100-150$ - not a necessity but it makes life A TON easier
nutes - fox farms solubes/tiger bloom/grow big - 90$
ph up and down - 20$
hydrogen peroxide 3% or h202 concentrate that needs to be diluted - 10$
If you do it right for less then 600$ you could have one bad ass dwc closet grow. Just my 2 cents. Hope it helps and throw up a journal when your ready