Gordon Freeman how old is he?

[AJ Rimmer]

Excuse me but when did the Gman "find him"?

I guess he means when the G-man teleported him from Nihilianth to the elevator thing and the endgame began.
@alec85: Exactly, which is what makes HL brilliant, because if Gordon has been in stasis, or coma for ten, fifteen years, what have you, that means he doesn't know diddly squat about the situation. Just like you.