There was a image someone made before that was a guideline of future updates. I'm not 100% sure how it went, but it's similar to this.
Alpha Members --- Updates, addons, future expansion packs etc...FREE
Beta Members --- Updates Free? Everything else must be payed for.
Post Beta --- Pay for everything?
I really am not sure. I know Alpha members (which is what I am) get everything for free for life. Everything else I'm not sure of.
If you bought the game now, you'll be beta.
Credit card - If you buy the game with a credit card, the payment will be made, and you'll be able to download the Game on the site, I don't believe there is any email stuff. I didn't have to deal with that, but you might depending on your card and what not.
Alpha > beta > full game > minor fixes > major fixes > exp packs > addons
Beta > beta > full game > minor fixes > major fixes MAY GET> exp packs > addons
Full game > minor fixes > major fixes <HAS TO BUY> exp packs > addons
it seems people only read the has to buy, you MAY get addons and exp packs, but there is a chance you will have to buy them