Seva, have you ever visited Jacques Fresca's The Venus Project, in Venus, FL? If you are close enough, it would give you GREAT INSIGHT into what is possible. He and his partner built several demonstration domes themselves, using simple construction with self-built countertops and interesting flooring.
www.thevenusproject.com
His model for sustainability, designed around PEOPLE-CENTERED ideals, is showcased at their 25-acre site. Well worth a trip for all the ideas it will spark.
To give you some idea of how much land, I'll share some specifics from a 34-room Retreat Center we built on an 8-acre site in the mountains of NC. We had an average of 75 guests per week, plus 25 staff members, who lived on-site. We ate all meals together in the central dining hall. 100 people was a very workable "community."
The central dining room/kitchen/main office/manager's apartment with a basement laundry and dishwashing center, was approx 120' X 60'.
Within walking distance of the main building, we located 3 lodging units, two 10-unit two-story lodges with efficiency studios 27' X 12', and one building with 10 rooms and a 2-bedroom manager's apartment, with 4 units on the upper story, each room 28' X 12', for a total of 34 rooms and 2 2-bedroom apartments.
There was plenty of parking at each building. A paved one-way road allowed a beautifully landscaped natural area between each building. We used mostly native azaleas, rhodedendrons, and mountain laurels which we carefully transplanted from the nearby woods.
Over the years, we added a kidney-shaped pool, a hot-tub, a 100-seat amphitheater and stage area, another conference room of 30' X 60', an exercise room, approximately 20 campsites with bathhouse, and a small orchard for dwarf fruit trees.
THE 8-ACRE SITE WAS NOT AT ALL CROWDED. It made excellent use of a hilly site, so that nobody was too far away from the main building to walk to meals and main activities.
On our 8-acre site, we could have built at least 5 domes per acre, and landscaped for privacy so that each would be practically invisible from the other. I loved the way the domes were designed at The Venus Project. Some domes are too tall and gangly. The ones Jacques and Roxanne built at Venus were one-story affairs utilizing a smaller footprint that blended beautifully into the surroundings. They would be a dream to set up for off-grid living.
We, too, designed and built our complex ourselves. It is so satisfying to tackle such a project. If you don't know how to do something when you start, trust me, you'll learn far more than just how to build a building.
We were probably a little more hilly than some of your sites in Virginia or Kentucky or Tennessee. Climate throughout that region should be ideal for GC communities. Unless you are spoiled by the climate in Florida, where, with the proper "dwelling," you never need a heater or an air-conditioner!