hey, are you in a climate that gets snow? if you are you might want to know that the lighting will melt snow, and you will be the only house without snow on it, this is what's keeping me from growing up there.
you can tap into the water source, but I would make sure you put some type of drain up there.
the lighting will be dependent on how wide and long the space is.
you should plan on one light every 6-8 ft. down the length of the space.