One of the largest portable grow rooms at Groindoor.com is the 8X16 grow tent. You will need to set them up in a large garage or warehouse to make sure they are set up and can function properly. The grow room offers much more efficiency to the grower in terms of management, especially considering the tent can house as many as 50 large and 64 medium-sized plants.
Are you thinking of purchasing a complete kit? The best thing you can get is an 8X16 grow tent kit that comes with grow lights that can cover the whole tent, a fully functional ventilation system, a grow setup, and other accessories to an aide during different stages of the grow cycle.