Sorry but the law in your state says I can sell up to 4 per year if I become a resident.
Yeah, it does. So you're safe with the state.
Unfortunately, federal law says that if you're selling guns to make money (even four or less) then you're in the business of selling guns, and if you don't have a Type 01 FFL, then you're in violation of federal law.
People here have been busted for it.