Lurking Evil

• WWizards of the Coast2004-10-04
  Official Ruling
  When it turns into a creature, it is no longer an enchantment.
• WWizards of the Coast2004-10-04
  Official Ruling
  If you have zero or negative life, half your life is zero, so it costs nothing to use the ability.
• WWizards of the Coast2008-08-01
  Official Ruling
  A noncreature permanent that turns into a creature can attack, and its abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.

Rulings via Scryfall