My personal preference would be for a timber framed house with straw bale in-fill. Despite all the naysayers, those houses have been built everywhere - starting in Nebraska in the 1800s. There's one in Georgia that was built in the 30s that looks neoclassical - you wouldn't know it was straw bale construction, and it's still there, despite the humid, hot, damp climate.
Water is the primary concern, so your foundation would need to be several inches above ground for the first row of bales. The eaves should extend out to maximize the protection of the walls. Having said that, the walls can handle typical wet / dry cycles.
The walls are reputed to have an insulation value of R35. Straw bales will not burn easily because of the low oxygen content within the bales. If you use concrete stucco within and without you have a serious building.
You might also consider "rammed earth" construction - there are houses in Europe that are hundreds of years old that were built this way. You mix sand, a little clay, a little water and maybe a little cement as a stabilizer, and shovel it in thin layers into a form where you pound on it with a rammer. You repeat this process until you fill the form and then you reposition the form; repeat the entire process again and do it until you reach your final wall height. You are basically making sandstone walls. Parts of the Great Wall of China were built using this process too.
The major expense is not the walls of the house. It is what goes inside, under, and over it: kitchens, baths, flooring, electric, plumbing, land, foundations, roofing, etc.
What intrigued me was that for those in the third world these types of housing could be built by families and could provide very inexpensive a safe shelters.