How do i buy minecraft mods?

You don't buy mods. How old are you?!

They're free, just google search "Minecraft mods" and hope you don't get a virus.

Depends on what you mean by Mods.

On the PC for the full version of Minecraft, mods and skins are free. Installing them is more difficult, but they don't cost anything.

The consul version of Minecraft sell skins for characters and 'texture packs' which changes the way the game looks. Those you buy from the consul's online shop.