1- quite a while. I got my first gun around 12 yrs old. I had a Remington .22 and Winchester 94 30-30. Got a shotgun when I turned 18. A .22 pistol at 21. A Remington 700 .270 shortly after. on and on
2- since around 12, OK technically I could not "own" them but I was the only one in the house to use them. And I was free to get them and hunt whenever I wanted.
3- 15, 4 pistols, 4 shotguns, 2 muzzleloaders, 3 .22 rifles, and 2 long rifles. Yeah, I'm a gun nut. No assault rifle yet though, my only evil black gun is my G19.
And get a .22 pistol, they are great at the range!