In NY, handguns have to be registered and unregistered the counties of both parties. Each county has different rules regarding it.
Ulster County, New York:
--Pay seller for gun, get bill of sale containing his permit number and yours, plus make, model, caliber, and serial number of the gun.
--Take bill of sale to pistol permit bureau at Sheriff's Office.
--Pay $5, sign the form they stick in front of you, hand over the laminated card that lists all the handguns you are "permitted" to carry.
--They go to their magic machine and print out an updated card with your new gun added to it. They hand it to you along with a coupon to take possession of the gun.
--Back to seller. Give him the coupon, he gives you the gun.
--Seller takes the coupon to his county issuing authority, hands it in, gets his permit card updated to remove the gun he just sold you.
It gets easier each time you do it. If you plan it right, it can all happen in about half a day, especially if buyer and seller are both Ulster County residents and go to the permit bureau together.
What gets weird is if it spans over a few days, like right now. I just bought a handgun in a private sale. I have paid for the gun and done all the paperwork. However, because of work schedules, I can't pick it up from the seller until Monday. So right now he has my money
and the pistol, which is listed on both his permit and mine. I trust the guy, but it's a weird kind of limbo.