First, I am not a lawyer and cannot give you legal advice; this is only based on my personal experience.
NC requires a pistol purchase permit in order to buy a handgun. I was told in a class I took that even for a private firearm sale, trade, or even a gift in NC, there are certain requirements and permits required.
I found this quote at NC Firearms Law
"Under North Carolina law, it is unlawful for any person, firm, or corporation to sell, give away, transfer, purchase, or receive, at any place in the state, any pistol, unless the purchaser or receiver has first obtained a license or permit to receive such a pistol by the sheriff of the county where the purchaser or receiver resides, or the purchaser or receiver possesses a valid North Carolina-issued concealed carry permit. This requirement to obtain a permit prior to the transfer of a pistol applies not only to a commercial transaction, typically at a sporting goods store, but also between private
individuals or companies throughout North Carolina. N.C. Gen. Stat. § 14-402(a)"
You can look at the actual law itself at GS_14-402
Again, I cannot give legal advice, but this seems to indicate simply swapping guns within the state and without proper permits on both sides would be in violation of state law. You don't want something to come of this later. The local gun store I visit in NC has certain paperwork that must be filled out whenever a gun is sold and they must retain the pistol purchase permit or record the CCW permit information (that can also be used to purchase handguns.)
Here is an option that you may consider and talk to your local FFL about. My local gun store occasionally sells guns on consignment for individuals who are looking to sell their weapons. The dealer meets all the state and federal requirements involving the sale, retains the NC permit or records the CCW information, and finds a buyer (although in your case you already have a potential buyer) in exchange for a percentage of the sale. Anyone receiving a gun in such a transaction would still require a proper state issued permit. I imagine you could also ask the dealer about checking the serial to make sure it isn't stolen before you buy it (if that isn't already a legal obligation he may have.)
I don't know anything about private sales/transfers not involving a FFL and whether or not there are any other requirements if both of you do already have NC permits or NC CCW.
Keep this information in mind, but get your legal advice from the appropriate North Carolina agency, FFL, or lawyer.