Plastic is cheap I bought a 10 by 100 .8 mill clear plastic a Wal Mart today for $6'50. I plan on making frames for my cold frame beds using 8 foot 2by 4 and wrapping a layer on each side to have a double layer of plasic on a 4 by 8 frame! Thin film will work for 60 days! This frame method works great for a greenhouse also except use 4 mill or more for your plastic!
+++ A 10 by 25- 4mil clear plastic at Wal mart is around $7 and will do three 4by 8 greenhouse pannel. 2 by 4 8 foot are a $1.50 each 3 per pannel! That would be $4.50per pannel. Three pannels would cost $13.50 plus $7plastic or about $20 for three pannels or one 12 foot side of the greenhouse. You can build a 12 foot long A frame greenhouse for $40 plus plastic or a door for the ends of the greenhouse!
+++Depending how you angle the A frame you can make the inside 5 to 8 feet wide and about 6 to 7 feet high! A 60 degree angle would makeit about 8 feet wide and 6-1/2 feet high at the center.. Fasten it down with a few pipe!! A 24 foot 8 foot wide greenhouse for less than $100!
+++There is no reason to be wiithout one! Assembly tiime a few hours with nails and staples. Get a few five gallon buckets filled with water and you now have a 2 wall solar greenhouse! Two people can move this 12 foot green house easily once the ends are connected! You may need a few extra 2 by 4s for the ends!
+++One last point is that a A frame is a triangle one of the strongest structures you can make! Also new plastic from a 20 by 25 foot roll every 2 years will cover the outside of the greenhouse in one piece! If panels are screwed together they can be taken appart easily! Adding pannels is easy make it longer every year!