You can buy shotguns and rifles out of state, but not handguns. Also, some states have individual restrictions, so you should check NJ and PA law.
There are licenses and licenses. You can get a firearms owner's ID that will permit you to purchase and possess a rifle, shotgun or bb/ pellet gun at 18. A handgun permit is 21. A permit to CARRY a concealed handgun is 21.
By becoming a NJ resident.
Contacty your local police for current information.
NJ requires licensing of handgun owners, and police approval of all transfer of ownership of handguns. You need to discuss transfer on an inherited handgun with the NJ State Police.
you can't
If tou are a resident of NJ, then you apply in NJ.
no
Yes, but I believe NJ requires a Firearms ID card to possess firearms in the state. You should probably check with a local gun shop or police department to see what you need to do.
Both places. You file as a resident of NY, using that form, and as a non-resident in NJ, using that form (a 1040-NR I believe).
yes
No.