What are the requirements to buy a gun?

Answer 1

Depends on the gun, and where you are- laws vary place to place.

In the US, to buy a gun from a dealer, you must be old enough (18 for long gun, 21 for handgun), You may purchase a handgun only in your home state. You will need at least 2 forms of ID that show your address. At the dealer's, you will complete a questionaire (Form 4473) regarding criminal records, mental health, etc. The Dealer will conduct a computer or phone based background check with law enforcement. In some states, you can pick up your firearm as soon as the background check is approved- others have a waiting period of up to 10 days.

The 2 ID thing depends on where you are. Most states in the U.S. you only need one government issued picture ID with your current address, such as a driver's license or handgun permit.