Bucking the trend of bigger is better, Jay Shafer started a company specializing in designing and building small yet functional homes:
... since 1997 I have been living in a house smaller than some people's bathrooms. I call the first of my little hand built houses Tumbleweed (top left). My decision to inhabit just 100 square feet arose from some concerns I had about the impact a larger house would have on the environment, and because I do not want to maintain a lot of unused or unusable space. My houses have met all of my domestic needs without demanding much in return. The simple, slower lifestyle my homes have afforded is a luxury for which I am continually grateful.
This one above is called the Vardo, inspired by gypsy caravans and shepherd wagons, that you can build for about $4,000.
Link - Thanks Katia (good luck with the mortgage!)
They're made from reclaimed materials, and they have nice old-house architectural details. I've seen these things in real life, and the photos don't do them justice. They're pretty great.
http://www.tinytexashouses.com/
Has a similar lifestyle. She has made lots of interesting productivity and lifestyle enhancements, using recycled materials in a 100 sf home. She has a great photoset at flickr.
No kids.
No prospect of either.
All the time in the world for hobbies.
Staceyann C. Dolenti