One of the biggest issues in society is the cost of housing. Hundreds of millions of people can’t afford housing (even in the US, Europe, etc.). So, there’s a huge demand, but a lack of affordable supply. Here is a prime business opportunity for those who are knowledgeable about earthbag building, since earthbag (sandbag) houses are strong, low cost, durable and can be built to match virtually any style.
Whoever builds good quality houses at an affordable price will be swamped with orders. It almost doesn’t matter how you do it (cluster development, spec building, building to customer specifications, etc.). The key is providing the right house design at the right price. With the right plan, you could build a small, simple house every few weeks, sell it and build another one, over and over and over. (Example: Double Wide Earthbag House Plan, a house that mimics trailer houses, but can be built on the ground.)
While competing builders use expensive manufactured materials like plywood, 2x4s, fiberglass insulation, sheetrock, concrete foundations, linoleum, etc., you could build with low cost natural materials like earthbags, rice hulls, earth plaster, floors of earth, stone, recycled brick or tile, and so on, and sell at a lower price. Sure, people will have some uncertainty about buying a house made differently than the norm, but at the right price they will come around. The bottom line is people need affordable housing and virtually no one else is offering it.
I would look for a small town with minimal building codes to speed the process along. Find a community who is receptive to these ideas and isn’t totally destitute. Make sure you have a house plan that people like! Build one or two earthbag houses to get skilled at the process and refine your techniques. Have an open house, rent a booth at a home show and start taking orders.