Plague of Vermin

• WWizards of the Coast2008-05-01
  Official Ruling
  The amount of life a player may spend must be equal to or less than that player's life total; you can't spend life you haven't got.
• WWizards of the Coast2008-05-01
  Official Ruling
  In a Two-Headed Giant game, each player on a team gets a chance to pay life. The team's life total is adjusted in between.
• WWizards of the Coast2008-05-01
  Official Ruling
  If a player chooses to spend life, their life total goes down immediately. This will affect how much life that player can spend the next time the process gets around to them. If a player chooses to pay life three different times during this process, for example, that counts as three separate instances of losing life, not as one.
• WWizards of the Coast2008-05-01
  Official Ruling
  After the process stops, the total amount of life each player paid this way is calculated. That's how many tokens each player gets. All the tokens enter at the same time.
• WWizards of the Coast2008-05-01
  Official Ruling
  In a game of N players, the process ends when all N players in sequence (starting with you) choose not to pay life. It doesn't end the first time a player chooses not to pay life. If a player chooses not to pay life but the process continues, that player may pay life the next time the process gets around to them.

Rulings via Scryfall