It depends on what you mean by "sell". If you mean put it on Ebay for trade, or on PBnation then no. you have every right to do so. If however, you mean to open a shop and sell goods then yes.
No you don't. though you have to be 18 to buy one, under that age you can be supervised by a adult while using it.
Not in the US at least, they are sporting equipment not firearms.
No. No firearms permit is required for paintball guns.
You do not need a firearms lisence for a paintball gun.
yo dont need one
You don't need a license to carry a paintball gun in the United States. To purchase a marker you must be 18 , to play at a field, insurance requires that you be ten, but can sign a wavier for yourself at 18.
No there is no licence required to purchase/operate a paintball marker. In order to play you must be at least ten (at most places) and 18 to purchase a marker, balls, or CO2.