Look on Ebay for affordable tents. I found one under two hundred that uses 600D Oxford Cloth. Super safe and natural, all metal construction.

REFLECTIVE 93"x47"x78" HYDROPONICS GROW TENT ROOM BOX W - eBay (item 370460452337 end time Dec-03-10 10:50:14 PST)
joshmadwisco Reviewed by joshmadwisco on . Setting Up A New Grow Tent!!! So since one of my girls came up stolen this year I have decided to start growing indoors from now on. I have been on hgt.com and came across some grow tents that are really interesting!! Am pretty sure I found what I want for xmas!! The 56?x56?x78? GROW TENT features: Sturdy Steel Frame Measures 78" tall x 56" deep x 56" wide Heavy-Duty Light-Proof Black Ballistic Nylon "Skin" Shiny Silver Ultra-Reflective "MYLAR" Lined Interior for superior light reflectivity and dispersal FIVE Rating: 5