I JUST built a veg box yesterday. OP, look at the links and stuff below. I built a double veg box for ~$200. Could have been cheaper, but I bought everything the day of and didnt price shop around.
OK,
The cabinet:
http://www.lowes.com/lowes/lkn?action=productDetail&productId=90990-84396-17182939&lpage=none
I have only the middle shelf in it, so it gives me two ~3' grow spaces. I also got this for $81 in store.
Lights:
http://www.texashydroponics.com/shop/product.php?productid=2927&cat=286&page=1
I am running 3 of these on each level. I have 2 small chains holding them up.
Fans/Air:
I bought 2 cheap computer fans. I took an exacto knife and cut out the exact size holes for 2 fans in the back and placed them in their for intake. I also have a small fan inside the cabinet.
Reflection:
It is made out of plastic, so I lined it in tin foil for now. After this grow, I am going to paint the inside with down white.
I will put some pics up later maybe. My camera is next door in my real grow room. But in this setup for about $200, I am able to grow 10-15 plants in 2.5-3" net pods, up to 3 foot tall. Once I harvest my first main crop I will probably build 3-4 more of these and dedicate my tents to flowering, and leave these for veg, mothers and clones.