I just got a what is really a LNIB G19 and here's the kicker: previous owner says it has had about 1K rounds through it. Dosen't feel like it to me. Only the standard barrel wear tells the story.
Check your state laws about ownership of handguns at under 21.
Here in Texas it's possible for a person to PRIVATELY sell you a handgun in a FTF, provided you are over 18 and over and a resident of Texas (having no criminal records goes without saying).
As long as his intention for buying it in the first place was not to sell to another person, it should be good.
I'm 19 and currently own a G19. However when I was 18 I've had several Glocks pass though: G23, 2x G17, a previous G19, a G26. As you can see, I finally setteled on another G19. One of the sellers to me was a LEO, so it's okay in Texas. Be sure to check your state laws.
And it is true in some states they'll issue CHLs to persons 18 and over. Not sure of the states off the top of my head, but I know there are some. In addition, I believe that Texas has passed a new law that allows military personnel 18 and over to obtain CHLs.