Let's say someone were to purchase a small lot of suitable land, and
wanted to construct the lowest possible cost building possible, with
the following requirements:

-- Must be compatible with standard north american suburban building
codes
-- Size: Around 1000sq. ft in one floor.
-- Access door/stair must stay accessible year round in a northern
climate
-- Power, Telephone, Cable, Water and Sewer connections
-- Doesn't need finished interior, could be concrete walls/floors and
exposed wiring and tubing on the ceiling.
-- Doesn't need internal separations
-- Ceilings at least 8-9 ft high
-- Structure must be waterproof
-- Structure must last many years. At least 30, but more would be
better.
-- It should be possible to make it "nicer", post-construction. That
is, add proper flooring, ceiling, walls, separations..


I'm thinking something along the lines of an
underground/semi-underground bunker, non-hardened. Think of a normal
house's basement.. Maybe it could be buried, and grass would grow
above it - except for the ventilation and wiring, and the access
point. But it could be anything else.

The question: what kind of building can suit this purpose, and at what
approximate cost it can be built. Or ressources indicating that kind
of information.

Thanks.

Greetings!

There is an entire style of housing dedicated to living underground,
or semi-underground.  To fully answer all of your questions is outside
of the scope of Google Answers, but there is a book available that
does:

http://www.baproducts.com/50-house.htm

Also, the Complete Book of Underground Houses will be helpful:
http://www.baproducts.com/underhse.htm

There is a good deal of information available from the US Department
of Energy:
http://www.eren.doe.gov/erec/factsheets/earth.html

Also, the American Underground Construction Association will be a
great resource on this project:
http://www.auca.org/

So, to answer the first part of your question, you can really build
any kind of house you'd like, from an elegant retreat to a cement bomb
shelter.

You also inquired as to the costs of building such a place.  We'll
work with the assumption that you don't want gold plated faucets and
rare hardwood floors at first.  :-)  Building an earth sheltered home
will be somewhat more expensive than traditional frame construction. 
I have found one builder that quotes a cost of about $75.00 per square
foot for underground home construction.  Thus, at 1,000 square feet,
you would be looking at a $75,000 cost.

His brochure and website are at:
http://www.undergroundhomes.com/brochure.html

Another home built in Colorado cost $130 per square foot, with many
luxury options and built in furniture.

http://www.rmi.org/sitepages/pid379.php

Additionally, if you want to build it yourself, you can get the costs
down to $10 or $15 per square foot.  The following website details one
construction project on a severe budget.  Right at 1,000 square feet,
too...

http://www.daycreek.com/dc/HTML/TMEN_No67.htm

I hope this has been helpful; it certainly has been a fun question to
research.  If you require further information on your new home, please
feel free to ask for a clarification.

Search Terms:
build underground house
earth sheltered house
earth sheltered house building cost
earth sheltered house building cost square foot


Related Links:
http://www.liquefaction.com/berm/

I think these guys might be able to quote that job for you. 
Muahaha.. Muahahaha.. Muahahahahahahahahahaha!!!! <*CHOAK* *COUGH* *COUGH*>

Villain Supply "...your best online source for everything EVIL."
http://www.villainsupply.com/lairs.html

googlebrain-ga
"Evil will always win, because Good is Stupid." - Dark Helmet

http://www.calearth.org/3vaults.htm