Well, now for what i would do if money was an issue and i wanted to grow 4 plants. I am assuming that you have at least a 4x4 space to flower in. I will let you find a way to veg because if you use the same space for both and you are growing for personal this will work fine and produce way more then you could smoke.

Here is what i would use and what i would expect.

600W HPS with quality hood and ventilation= $500
http://www.1000bulbs.com/products.ph...ressure-Sodium
http://www.bghydro.com/BGH/itemdesc....HLRESS&eq=&Tp=
http://www.1000bulbs.com/products.ph...-Watt-Hortilux
http://www.bghydro.com/BGH/itemdesc....FSC082&eq=&Tp=

Hydro system = 200
http://www.usplastic.com/catalog/var...iant%5Fid=3827
http://www.angelsplus.com/Alita.htm (the AL 15 for 125)
Tubing and connectors are cheap and available anywhere

Air filtration and movement - $300
I would use the carbon filter fan to move air in the room as well.
http://www.bghydro.com/BGH/itemdesc....BDFS03&eq=&Tp=
http://www.bghydro.com/BGH/itemdesc....AEFE06&eq=&Tp=

Then you have nutes and medium and all should be good. That is the basics i think one could very successfully manage a closet grow with. I would assume that each harvest would produce at least 1lb+ if you paid attention to what was going on. Feel free to ask and I will help with what i can.