I want to grow 2 white widow plants,Inside a cupboard. White widow is excellent smoke, good choice

I am not to sure of what i need but i have an idea.I will add what i will be getting and more experienced users can advise me.

6ftCupboard which is 2ft by 2ft. About the right size for 2 plants.

I will then paint the inside of this white to help reflect the light. Good. Flat white paint or mylar.

For the light source i was thinking of using 250watt HPS bulb. Everythig was going fine until here. Of course you can use HPS, and it is the prefered light source, but it complicates matters quite a bit. You mentioned fluorescents before, and perhaps you should stick with it, unless you are prepared to spend some serious money on ventilation, and some time installing it. With HID you will need to suck cool air into the cabinet, blow it directly over your light, and have a big fan to suck all that heat to the outdoors. Better yet (and you may have no choice in the matter) is to have a cool tube, where an enclosed light has a dedicated ventilation source, in addition to the cabinet ventilation. In the small space you mention, it will quickly heat up to unacceptable levels. If you use fluorescent you can get by with one oscilating fan and that's it. A whole different (and smaller) can of worms.

To water the plants i would use rain water at the correct PH level. Fine, good. Don't forget to feed your plants, preferably with each watering, and adjust the mixture to 6.8 PH. PH meters are about $25 on the low end.

As its a tight space i was thinking of using a bathroom fan to suck in clean air(Does this air have to be from outside the house) You would only have to do this if you use HID lighting, and it would not have to be from outdoors, just someplace cool, probably close to the floor (since heat rises). With fluoros, you could put a small fan in the back, and crack the cabinet door a little. I am using fluors for some mothers in a closet and have NO fans. I just leave the door open about 3 inches, and they are doing great.

For the soil and plant food i would buy from my local gardening center. Doesn't matter where you get it, just don't get the kind that have fertilizer added. You can't control feeding with that kind. Don't forget: no ferts the first 2 weeks after sprouting, and then only 1/4 strength to start.

Should this be enough i understand white widow is not to difficult to grow It's enough for a starting point. We've scratched the surface. We have not considered lots of stuff, such as odor control, if that's important. This changes ventilation plans considerably. The best thing you can do at the beginning is read the FAQs and any other grow guides you can get your hands on. Especially do this if have a question on basic stuff. The forum search engine is real handy too. Just type the subject of your question, and you often have a bunch of answers. Overall we're glad to help, but people are not going to want to answer the same beginner questions that have been asked hundreds of times, when the answer can very easily be found by 5 minutes of searching.