Very good advice so far.

IMHO. If you are a beginner...DO NOT get the biggest light possible. Big lights put out A LOT of heat and beginners have plenty to worry about, don't add heat problems to that list. I started with a 400w and have never had serious heat issues. I now have 2 400w (800w total) and i still have very little heat to deal with. 600w would be the biggest i would go for a beginner. And even then you'll get a good taste of what the heat can do.

as far as your electric bill...it's hard to say because we are thousands of miles apart. But my 2 400w lights are about $40 a month.

I would also veg with CFLs or fluorescent tubes until you get the hang of it. Metal Halide is great for VEG but it's a lot more power and still lots of heat.

That NFT system is pretty rough for a beginner as well. The simplest system i've ever used is a 5 gallon bucket DWC. It's a 5 gal bucket, an airpump, and an airstone. that's all. no moving parts...no moving water...just sits there and grows big as fuck.

good luck and keep us posted.
Skeet.