lol, Yoshi365.... you do NOT buy updates. Please know the information you are stating before releasing it as common knowledge, in the highest case, to a new player as well.
I have been playing Minecraft since BETA 1.6, so this answer is 100% true.
Once the update is released, you log in. It will then say there is an update available for Minecraft. Select yes if you want to update, no if you don't. Simple as that. No payment required.
Visit mojang.com to read the snapshot update log. Pretty much there's going to be ender chests (I like to refer to them as traveling inventories), desert and Jungle Ruins, trip wire, a new creative mode menu, a new world type (Large Biomes), simple LAN connection multiplayer, and writable books. Let me know if I have forgotten something.
