Cleaning out old emails, I found a few links of interest to those who would like a set of building plans for a small hoop greenhouse. Both provide photos, diagrams and list of materials with approximate cost to build.
From North Carolina State University Extension services - 12 by 14 foot = 168 sq foot
From Washington State University Extension services - 10 by 42 foot = 420 sq ft
And, the originating document about row covers and hoop houses is also a good read