Fade Away

• WWizards of the Coast2004-10-04
  Official Ruling
  At the beginning of the resolution, each player counts up the number of creatures they control, then they make the required number of payments and/or sacrifices. The active player announces their choices first followed by the other players, but all the sacrifices are done at the same time. Because of this, you can’t sacrifice one creature in order to pay for another and thereby avoid payment for the first.
• WWizards of the Coast2004-10-04
  Official Ruling
  You can choose to pay some mana and sacrifice some permanents if you have more than one creature.
• WWizards of the Coast2004-10-04
  Official Ruling
  You can activate mana abilities during the resolution if you decide to pay mana.

Rulings via Scryfall