There's a flashback of Tidus' with him as a little boy where he has a conversation with Auron about the impending death of his mother. And the pilgrimage really can't be that long. Going by FFX, it's even less than a month. Spira is pretty small, ya?
I've played FFXII, and Vaan is a street urchin who does chores for an elderly shopkeeper for food. He'd also have been screwed without that handsome rogue Balthier.
By the way, judging from the early parts of the game, Tidus is hardly a resourceful person. "I need food!" "H-hey, don't go out on me!" "nom nom nom no- urrrk! Hot! Hot!"