Aloha, I've lived in Puna, B.I. about 10 years and lived here previously. You might try the forums at: www.punaweb.org It is based in Pahoa. There are several people posting there that have done what you want to do. There are discussions about building, farming, volcanoes, vog, off grid living, etc.

This is much appreciated advice. We will follow up and visit the puna forum. Mahalo

Aloha Richard.
I have recently moved to Puna.If you love gardening as much as I do, you need to make sure that you look for land that has deep soil. Try looking up at higher elevations between Hilo and Volcano. It is cooler and wetter at higher elevations. I can't express how much fun it is to garden in a yard where you can pull large weeds out with your hands with an easy tug. Digging to plant trees or shrubs is rediculously easy and fun. Watering? Hardly have to give it thought.. comes from the sky! There is a heaven on earth for gardeners and I feel blessed to have found it in Puna.
Good hunting!!