Tom and Debbie,
What I did may not work for you, but if you want to see how it was built go to my profile and look at my albums (many more photos).
I had this built by a guy that had a saw mill. All the wood is 1" or 2" rough-sawn, which cost much less than lumber yard wood. The base is 4"x6" Pressure treated. The total cost to have it built was $5,600. (I leveled the land first). I am sure in Vt. you have some saw mills. It is 20'L x 14'W x 14 1/2'H, with a 3/4" gravel base. It is open under the overhangs (with screening to keep the birds & animals out) plus end vents, to give it good ventilation. I know yours has to be much larger.
To me it was the best investment I could have made. Now 6yrs. later my Que looks the same as when I bought it. (I only use it 4 or 5 wks. a year).
I think it would be much better to add sides to what ever you get, if at all possible.