If you get caught with a gun that hasn’t been transferred to you legally, you BOTH go to jail. If it was used in a crime, you both are punished equally for the crime. 
All firearms should be registered. I can’t see a situation where it would be unnecessary. The money used for registration can be given to the innocent victims of gun violence.
Yes, if they want the privilege of owning a gun they should pay for registration as well. We do the same for cars and those are arguably actually required for a lot of people to work and live.
You can buy a car at any age, without registration or a license or insurance, you can transport it across state lines with no issues...and then drive it on private property with no restrictions. The car analogy is a terrible one