Although I have no first hand experience in this, it has been reported here on BP that Dallas homes are very prone to foundation problems because of the underlying soil. 

some pools are sinking, breaking away from their coving, empty spots underneath, cracks…you name it.  

The Labor is tough because time is money, also if the windows are rotten thru, the structure is probably compromised underneath as well.

A site plan generally starts with a survey, overlays the setbacks, may have topographic info, may discuss things like soil/erosion control, and ultimately will overlay the new square footage you plan to add, to scale and where you plan to build it.

The asbestos with tiles is probably underneath and not on the surface.

Rhetorical question.If the citizenship of the person is in question, do you apply Constitutional law if they are on US soil?

We are a nation of whiners and blamers now instead of one of doers and fixers.Agreed Bryan,Just because Bush is responsible for $3T+ of our debt and allowing the worst terror attack on U.S. soil doesn't mean he's the only one to blame.

Also, keep an eye out for an oil tank... in my neck of the woods they are one of the biggest issues with old houses and can cost thousands of dollars if they have leaked and the soil needs remediation.

.), is the lot infill, do you need to re-zone, are water/sewer available (if not, get a soil scientist to test the soils), impact/tap fees, etc. 

But to a GC, maybe it's not as scary underneath all of it?