By then, I will have a better assessment of the risk and may change my position at that time.

We just need more information to assess your situation. 

When searching for deals through a realtor or wholesaler and viewing homes, and not having that experience to just walk through a property and assess the rehab costs on my own, is it common practice to bring a contractor with you while doing a walkthrough to gage what needs work and how much it'll cost?

Will re-examine market value and assess any repairs at that time to determine next steps.

It'll be a few months before we can go in and assess any renovations fully though they are expected to be primarily cosmetic.

So county assessments are usually about 20% low.  

Go get an agent to work with you primarily because the seller is expected to pay for this transaction(this is true in many states, may be not in NC) You will get an experienced person who can help you assess pricing, negotiation and review other matters.

Also have to make sure the former mine has not been used for dumping (it is not uncommon). definitely would want to assess potential impacts especially if buyer wanted to change use... 

If so, you may want to seriously think about property tax implications to any transfers as well, depending on how low the assessed value is on these properties so as to keep the Prop 13 value and not trigger reassessment. 

The property was last assessed around 250k by the local tax assessor.