First, welcome to (relatively) free(r) America.
Here's what you want:
§21-1289.12. Giving firearms to convicted persons.
GIVING FIREARMS TO CONVICTED PERSONS
It shall be unlawful for any person within this state to knowingly sell, trade, give, transmit or otherwise cause the transfer of rifles, shotguns or pistols to any convicted felon or an adjudicated delinquent, and it shall be unlawful for any person within this state to knowingly sell, trade, give, transmit or otherwise cause the transfer of any shotgun, rifle or pistol to any individual who is under the influence of alcohol or drugs or is mentally or emotionally unbalanced or disturbed.
Other than that, cash and carry, handshake and a smile. If you want a bill of sale, or to see ID, that's up to you; the seller can impose any restrictions he wants. If it feels hinky, walk away. But, no one needs permission from the government to buy or sell a gun out here in the rest of America, and no one is going to track who owns what.