I want da funk!

Hi, I'm a new grower and am just now getting my closet up and going. I plan to grow maybe 3-4 plants. This is only for my use. I don't plan to make money or anything. I don't want to get all gung ho and obsessive about specs either, just a fun hobby w/ a nice payoff.

I do have some lighting questions:

With the size of my closet (5x7.5x1.5), how much lighting do I need for 3-4 plants during flowering. (also, if I don't use as much light as suggested, does that just mean my yield will be slower and less?)

Where's a good place to find grow lights? Any website cheap and secure?

Any help would be great.