Building Costs Estimates

Livable space (finished, heated) costs $100 per square foot as a ballpark entry-level (fancy materials naturally add cost).

http://www.home-cost.com/template.php?sectionID=10&pageID=44

A concrete foundation costs $2.75 per square foot plus $11.50 per linear foot of footings (on the perimeter).

http://www.absoluterv.com/concrete-foundation-requirements.htm

Star Group provides this useful list of typical costs:
(for California but they seem like a decent guide for throughout the United States)

HEATING / COOLING

	Install new forced-air furnace $2,500 to $5,000.
	Remove ducts with asbestos $1,200 to $2,400.
	Install new flexible ducting $2,500 to $3,500.
	Install new wall furnace $1,000 to $2,500.
	Install new floor furnace $1,500 to $2,500.
	Replace vent piping $600 to $1,200.
	Service furnace $250 to $500.
	Encapsulate asbestos ducting $1,000 to $2,000.
	Add central A.C. system $2,500 to $3,500.
	Replace condenser pump $400 to $700.
	Replace A.C. compressor $1,400 to $1,700.
	Service A.C. system $250 to $450.

PLUMBING

	Replace galvanized piping with copper $1,700 to $3,000 per floor.
	Install new waste piping to street $3,500 to $7,000.
	Reset toilet (excluding floor damage) $200 to $300.
	Install new toilet $350 to $450.
	Replace water heater $600 to $1,200.
	Install pressure / temperature valve $100 to $150.
	Elevate water heater on platform $200 to $350.
	Install sump pump $800 to $1,600.
	Replace shower pan $1,000 to $1,500.
	Replace tile shower $2,200 to $3,200.
	Replace faucet $150 to $250.
	Install gas line $40 to $50 per ft.

INTERIOR

	Painting $500 to $800 per room.
	Remove acoustic ceiling with asbestos $7 to $12 per sq. ft.
	Install masonry fireplace $7,000 to $12,000.
	Rebuild masonry fire box $600 to $1,000.
	Install prefabricated fireplace $3,500 to $6,000.
	Major bathroom remodel $6,000 to $12,000.
	Major kitchen remodel $15,000 to $60,000.
	Install battery smoke detector $50 to $75 each.
	Install direct wired smoke detector $175 to $275 each.

FLOORS

	Refinish hardwood floors $3 to $4 per sq. ft.
	Refinish softwood floors $9 to $11 per sq. ft.
	Buff and apply finish only $1 to $1.50 per sq. ft.

(Average room is 250 to 350 sq. ft., costs do not include removing and replacing furniture)