just my 2¢
i bought a cheapo amazon tent for like 80 bucks, 32x32x60 or some shit like that...put a 400w HPS in it and was able to flower out 3-4 plants at a time.
the cheapo amazon tent was just fine as far as quality goes, poles are a bit cheap but for the amount of money i saved not buying a name brand tent i was able to afford a roll of duct tape and toss a small piece around the joints where the poles fit into each other to keep them from seperating (my only issue with the tent) it has lasted me 2 years now and still growing in it. the materieal it is made out of seems pretty heavy dudty, it came with a insert for the bottom that work great....not saying cheap is always the way to go but i have for sure got my moneys worth out of this tent.
i agree with grorite aabove 4x4 and 600w will give you a fairly decent amount of room. i also agree with going soil for your first time, wise choice, i have been growing 2+ years now and the more i learn about hydroponics the more i keep shying away from it. without proper equipment its just a failure bound to happen and PH pens and PPM testers can get pricy for reliable ones.
check out apollo bran balasts and light kits on amazon, for the price they are pretty nice and thye offer a 1 year warranty on all bulbs and a 3 year warranty on thier ballasts. as you grow your going to want to expand your operation even if its just minor things like adding in a veg room or a cloning station but a 600w HOD and a 4x4 tent will get you off on a good start. dont forget your going to need to invest in containers, soil, nutrients, fans, temp/humidity gauge, ducting, carbin filter (if smell is a issue which it usually is even if your 100% legal no one needs to know your growing) extra light bulb (being stuck without a light sucks)
my advice to you is to write down a budget you need to stay within, then sit down and brainstorm every little thing you might need for this grow, research costs and see what you come up with. if you can still buy that expensive name brand ballast and tent after thats all done by all means go for it but it would sucks to put out all that money and then wind up too broke to continue your adventure.