i would say if u have a an a/c vent near buy u can take the vent off and get some 4 inch duct and run it from the a/c opening to the top/side of ur lil hut there that would be the cheapest. and get some cool air in there + it will be bringing in new air as u are doing this on the cheap and inline fans can cost some money u might have 10 to 20 buck invested in just the 4inch duct