Im assuming that the room is 8 feet long and 4 foot deep. Should be plenty of room. 500 bucks should be plenty of cash for this too. My favorite place for indoor supplies is www.insidesun.com . Their lights are cheap, but reliable. I would suggest that you get 2 400 watt h.i.d.'s at 90 bucks each, or 1 light, and a linear light mover,little more expensive, but will draw less power to run, in order to cover the area those trees will take up. Insidesun used to sell hydrofarms 4 foot linear light mover for 100 bucks, but they dont carry it anymore, I would do my best to try to find a retailer near you to get one. the 2 lights will be a little over 250 bucks, leaving 250 bucks for things like a vent fan, ducting, timers ect,ect.