The Modest Module
To build a $300 house requires a minimal use of generic local materials, a logical and simple installation process, and adaptability to family needs. The modest module built separately and then assembled together could achieve these goals.

Solution

The framework is based on standard 8ft and 10ft lengths of 2x4 wood, but it could be metal poles or bamboo. The use of diagonal framing to provide rigidity and lateral stability results is less framing required.
Fastening of the frame could use off-the-shelf brackets or even secured with rope to make the triangular "half" module which is set in place and secured to a second module to create the house. 
2ft x 8ft panels of local materials such as wood or metal are secured as walls to the frame, with door and window(s) located to suit framing.
The inverted roof collects water into a cistern. The roof panels could be rigid with a simple tarpaulin topping, or even just canvas, with the long central beam supported by rope from the two main posts.
The floor could be set on the earth or raised and simply supported on edge framing and beneath by blocking. A raised floor prevents flooding, pest infestation and provides passive cool air flow up through to high vents for air discharge. 
Repeating the module can create several rooms for a family and provide a courtyard when adjacent houses are constructed.

·         Customers struggle just to survive, so the burden of extensive labour may be the last thing they want or are capable of- my designs (The Modest Module,  and The Panel House) use  established technology, material and simple assembly processes to reduce the labour component.

·         Their varied life styles need a responsive house assembly that accommodates personal input �my design allows for the modular panels to be cut anywhere for windows, doors , vents, and to be able to temporarily remove interior wall panels to suit changing needs.

·         Security,  protection from the weather, a non toxic environment and comfort are basic desires by all humans- my design uses one modular panel system for roof, wall and floor to achieve these goals.

·         The progressive assembly process is designed to be fast and simple. Although not particularly innovative, it is responsive to potentially uninformed customers.

·         The costs to produce the stand-alone single house is in the range of $500, but with a 4 quad house the price starts to come down. Like most proposals, I have not included the cost for off-the-shelf window ($180) and pre-hung insulated metal door ($220). My design does have the attribute to use the cut-out panel portion as the actual door (edge trim would be required) and window shutter, which would help reduce costs.