{Snapcaster Mage} + {Ancestral Visions}
Can I snap Ancesral back for free?
Hmm. I think so. If it was just "cast target spell from your graveyard," then no, but since it says it's flashback is according to its mana cost, 0, then I would say yes.
Nope. Non-Existent Mana Costs can't be paid. Since Snapcaster specifically says that the Flashback cost IS the Mana Cost, there is no Mana Cost that you can pay, which is different than a Mana Cost of 0. If Snapcaster said 'of X, where X is that card's Converted Mana Cost', then it would work, but it would also stop the interaction of Flashing Back {Gitaxian Probe} at the cost of two life (and also be really powerful for flashing back spells for all colorless mana).
From gatherer:
10/15/2006 This has no mana cost, which means it can't be cast with the Replicate ability of Djinn Illuminatus or by somehow giving it Flashback.
True thanks guys!