Follow these instructions and you can make a money easy.

  1. Make 6+ Worm Food
  2. Have a Flail and Cobalt or Obsidian Shield
  3. Have full Molten Armor
  4. Have 200+ health
  5. Goto the Corruption
  6. Summon Eater of Worlds
  7. Hold Flail on ground (aim at legs, click and hold)
  8. Destroy Eater of Worlds without moving
  9. Collect money (+2000 copper, +100 silver each time)
  10. Repeat 6 to 9 until no Worm Food left
  11. Sell stacks of 99 Demonite Ore for ~8 gold.
  12. ???
  13. Profit.

When you destroy the head it drops the heart restoring 20 hp. More than it can damage you for.

Not to impress you or anything, but with 9 Worm Food I made over 1 Platinum in under 20 minutes.