Where to start?!

I'm a newbie here and am going through what i like to think of as a "practice run" right now. I'm growing in a closet with poor ventilation and no real way to control temp or humidity. But anyway, I'm in the process of planning a small grow cabinet big enough for 2 maybe 3 plants about 3 to 5 feet tall. I'm wanting to do this all myself since I'm on a budget. Can anyone tell me what the best measurements would be for a cabinet with room for just a few plants?

well im planning on growing in an 2 x 4 ft wide and 5 ft tall area which i think is perfect for 2-3 plants, maybe just two full grown. but im going to be using a lowryder strain so im thinking i could fit at least 3-4 in that kind of space.

I was looking into a 4x4x6.5 with room for a 4 gallon resevoir between my plant boxes

well in that case, if youre planning on buying a grow tent check this out

http://www.amazon.com/4x4x6-5-Hydroponics-Grow-Hydro-Cabinet/dp/B001GFQV10/ref=sr_1_3?ie=UTF8&s=home-garden&qid=1272003761&sr=8-3

this is what im getting but a smaller size. add a few pc cooling fans, growlight & hydro setup and you'd be good to go

depends on how you plan to light it. HPS/MH lights,if mounted horizontally, throw more light from the sides than from the end so a rectangular (SP?) cab would make better use of the light. for 2-3 plants,18x24 inches or so would be fine w/ a 150 HPS but this setup wont work well if you are trying for 5 foot plants as the light wont penatrate that deeply w/out a few CFLs.
I have seen a few old refridgerators converted to growcabs & they are nice because they are cheap,lightproof and dont look out of place in a basement or garage.add lights and venting & your set.

I'm not going to buy one but my roommate and I are going to build it..I came up with an idea last night but didnt sketch it out b/c i'm a horrible artist..anway its going to be 4x4x6.5 with a single 150 watt hps above and 4 27 watt cfls on each side wall 6500k for veg and change them out to 2700k for flowering. I'ts going to have the 4 gallon resevoir with 2 aquarium pumps to water both plants. Haven't looked into the ventilation much yet bbut have a pretty good idea on how i'm going to handle it!