Couple of questions: Is the property currently zoned residential and have you gone to the city building zoning and building departments to verify you can build on the site?
With the green building craze, this would be a very difficult question to answer. For instance, if you were trying to get the structure a LEED certification, part of the scoring would be what was done with the original structure. How much was recycled and/or used for the new structure.
There are some online constuction calculators available that might give you a ROUGH idea of costs for construction at http://www.building-cost.net/ (click on Start Calculator)
More information about green builders and green construction will be available in the AA area this fall or in Grand Rapids today and Saturday http://www.greatlakesgreen2008.com/
I highly recommend that you talk to some local real estate investors and people in your community who have experience in this area. Builders and investors in my area pay about $10,000 to tear down homes...in some cases...they work a deal to have the structure hauled away for free. It is all relative and just depends on what kind of opportunities you have in your local market. In bigger cities...there are lots of options.