Need help with ventalation

Hello, I am getting a grow tent that is 3x3x6.5 ft. And I will put a 400 w hps/mh light system, mh for veg and hps for flowering (it's interchangeable) and I am going to do a soil grow. What do I need for ventilation? What are my options and how much will it cost (estimate).
Thanks in advance.

Oh and by the way this is my plan to grow 2 plants, and I'm considering the scrog

I say get a 6inch fan with a fan controller then just adjust the fan to get the temp you want. Also cost depends on where u are Uk, USA ect

yeah, just an aircooled shade and 6 inch fan would do the trick. http://www.ventingdirect.com/inline-duct-fans-exhaust-fan/c11868 Soler and palau make the strongest most quiet inline fans

would i connect that to suck the air out of the aircooled hood? or is that to draw air in? and if it is to just draw air in, does that mean i just need a tube connected to the light and to and access point in the grow tent so it goes out on its own?