What do i need to grow here?

I think you have a bit of reading and research to do. There are so many variables to growing that there is no correct answer to your question.
Basically an area that size with 2 plants would only require a 250 watt hps. watch out for foil as a reflector. It doesn't reflect all the light spectrum back to the plants and can also cause light burns. Also you may consider the growth rate and strain you wish to grow. Your light will take-up some of your height and depending on the size and height of your grow medium, 50 inches becomes less and less, You can succesfully grow in that space, you are just going to have to manage the height of your plants. I had one plant this week that was a particularly vigorous phenotype, and it outgrew the other 4 by 6 inches once I started flowering. I had to bend and tie down the cola to avoid continuing to raise the light further away from the others. Anyhow......so many variables so many options. Look around on this site for scrog grows, or LST grows. That would work awesome in there. Make sure that closet has a good door on it. One that doesn't let light in or you may be dissapointed when flowering begins. (get inside and close the door with all the lights on in the room. If you can see light through cracks or seams, tape them or use weather stripping on door cracks. A good piece of advice a grower gave me was this...."build it all first, check your systems, veg cycle and flowering, check your systems again, then add plants" Flowering is the trickiest and the easiest to fuck up. DON'T LET LIGHT GET TO YOUR PLANTS DURING FLOWERING. THE DARKER, THE BETTER!

 

No prob. Plain white flat paint is an awesome reflector. Somewhere around 94%. i use mylar, but that's because a staple gun is faster than a paint brush. From what it looks like, you would have a harder time painting I think. Those rolls of mylar sold at most grow shops are a little costly. About $1.00 a lineal foot. (I think the roll I used was 5' high) i had to buy the whole roll for around $25.00. Another cheap way, but a little less effective, is to use those emergency blankets. They are sold everywhere. They cost around $2.00 or $3.00 but are extremely wrinkly. My first grow I used these and I didn't even do a very good job with the creases and wrinkles and hd no adverse effects. All I know is the more ways you can bounce the light back at the plants, the better. Sometimes I think micro grows and closet grows work so well because of that reason. Like I said earlier, I am trying totally fluorescent grow this time, but with tons of side lighting and reflection. my neighbor has several hps lights of varying wattages, but continues to place All his lighting above the plants in the middle of the room with no reflection or side lighting. He produces great weed so don't get me wrong. I'm just saying that sometimes you can produce the same product with less wattage and better light manipulation. Its not always about how bright, but what spectrum of light you are using and where it is penetrating. I too have a White strain growing. (white rhino) She is sitting in a veg tent with a couple others waiting for her turn to go into the flower room. Good Luck and keep everyone posted. Check out my grow if you want. Don't know how to create a link yet. I will be posting week 4 flower photos today. I have 5 NYC diesel plants. All of wich are very sativa phenotypes. They tripled during the first 10 days of flowering.