i agree with MaryDean, i think it's about what kind of space you have, rather than how much? If you utilise everything well, then you could probably afford to have a smaller house than if you have a massive house with just heaps of useless square metres all over the place.

i personally love the idea of straw bale houses, DH and i one day would love to have a little bit of acreage and build our own place, that would be awesome