I don't get the concept of a "tier 2 starter". A starter for when you're not actually starting? Or is it a starter that people buying the game post launch will have to pay extra to start as?

We're still working out many of the plans for post-launch, but the current idea is that the Reliant (and similarly priced 'tier 2' ships) would be part of slightly more expensive packages. It's 100% a ship intended to start the game, though! Like the Aurora and the Mustang, the Reliant was designed from the ground up to allow players to experience as many different opportunities in the Star Citizen world as possible.