i've got 3 hoophouses and a high tunnel. they are all tubular steel covered with 6 mil poly. i can grow veggies all year round in them with out any artificial heating. this is zone 7a. many farmers in much colder zones do the same. you can see pictures on my farm's facebook page...Indian Valley Farms. i bought a kit for the high tunnel that's 26x48. the kit cost $4600. it also cost to have the land leveled, endwall lumber, concrete for the ground posts, and endwall temperature controlled shutters. i built a 12x100 hoophouse using the johnnys bender (see it at the johnnys seeds website)and chain link fence top rails. total cost of that was about $2500. another hoophouse is 14x32 and the other is 10x48. the first step is decide what you want to grow and when, and if you want to plant in containers or in the ground. i plant in the ground.