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.

Buyer also would pay me $563 in property tax, insurance plus a small stormwater assessment fee for a total of $1400Based on my 15yr loan amortization schedule I will pay the bank $8,608 in interest over the next 3 years.

You can do drop and swaps which is a tax loophole which attempts to hide the sale from the school boards that try to file claims against the assessed value of your home, you can get a tax abatement in certain areas that will enable you to not have an increase in taxes for a certain amount of time, or you can purchase properties that already have the tax abatement on them.

Do you conduct property assessments?