1500 sq. ft. (Green Builders Award)..This straw bale plan won second place at the Green Builders Conference in Austin Texas a couple of years ago for the best energy efficient..low cost house. The judges really liked it...because of the charm, the many options including the upstairs rental. This was for a long narrow lot running north and the typical passive solar design was useless. This plan will accept winter sun at three level...each stepping back further into the house. And for charm...note the two level fountain/waterfall.
So what are these "options"? Well if money is a problem...the extension to the north for a shop/work area near the parking can be postponed until later. Initially, or at a later date, 1/2 of the gorgeous upper deck can be converted to living space for an upstairs apartment (inside or outside staircase), which can later be heated by the optional green house enclosing the lower patio. Lastly, the house can be built with or with out the clearstory/thermal chimney.
Yes, I know all these "options" are a bit of a streach...most people will never exercise them...but you do have choices up front...and anyway you decide go you get a great that functions...and can generate income.