Build .... 1.5 Inch pvc tubing ( i used 3 20 footers per arch every 6ft) couplings( straight connectors and t connectors) build base out of wood(2×6) to keep it square bend the pvc into an arch. Connect pvc with pipe.clamps screw them on the inside of the 2x6. Do 1 at a time and get t fittings to pr Ivide cross bars between arches for plastic to lay on .with everything in place and secure cover it with the thickest clear/cloudy plastic 8mil 12mil etc maybe 2 layers use a 1x2 or similar to secure plastic to base and thats your roof on the ends one 1 side build a door out of small wood to support some weight for a littlemlike 1x1 oe 2x2 door (whatever works for you.) mount 1 or 2 attic fan on 1 end( rmemeber to calculate e sqft for proper fans and ventilation) other end for vent were door is put in screen a few layers or old t shirts or fabric and put on door with a loose piece of plastic just draping down. When fans come on the plastix pulls from door the dabric is a filter and and there ya go 200 dollar green house. if you use 1x2 boards and screw to 2x6 and pinch plastic into place you can re use the plastic or staple it to 2x6 and buy new plastic each year. Add some electricity for fans for vent air cirulations and space heaters and there ya go