Typically, I wouldn't put OSB down but given that the T&G pine is underneath it all I don't see it as an issue. 

Some soils allow water to flow easily through them while others do not. 

@Xavier Randall When using the @name feature, as soon as you type the first 3 letters of the person's name an icon will appear underneath the reply box.

c) What are some things you could email the agent before hand to help you realize that this property might be "shady" or something bad underneath is going on?

I'm up at 7am making sure I have all my stuff together, including a flashlight and extra nasty clothes to crawl around underneath to turn off the water. 

Just having your broker's license does not make you an expert in the field and able to manage and advise other agent underneath you. 

If you don't have a detailed scope of work, finish schedule as well as a full list of what is excluded from the bid I can guarantee you that no one can give you accurate pricing.I can also tell you that construction, even ground up, has uncertainties, things from fluctuating lumber prices, issues related to soil, delays in getting supplies right now, and a bunch of other things that can causes prices to change during the course of a job. 

I came to realize that a ton of areas in the Texas have similar issues due to the quality of the soil. 

However just yesterday (after about 4 days of delays starting the work) my PM emailed me to tell me that the vendor said the line was underneath the root system of a tree that had been cut down and now the estimate was $3,500 as the vendor could not cut through the root system and would need to partially re route the line.First time managing a large expense and I have no reason to NOT trust the PM but I still feel like I should do something!

Directly underneath this box there will be a dropdown to choose from the person's name you are looking for.