Bladehold War-Whip's second ability reduces only the amount of generic mana in equip abilities. For example, it will reduce an equip cost of {1} to {0}, but it will have no effect on an equip cost of {G}.

The second ability affects other Equipment even if it isn't currently attached to a creature.

Some Equipment creature cards in other sets have reconfigure, a different ability that attaches them to a creature. Reconfigure is not an equip ability, and reconfigure costs are not reduced by Bladehold War-Whip's second ability.

The Rebel enters the battlefield as a 2/2 creature, then the Equipment becomes attached to it. Abilities that trigger when a creature enters the battlefield see that a 2/2 creature entered the battlefield.

If the Rebel is destroyed, the Equipment stays on the battlefield. Similarly, you may pay its equip cost to move it from the Rebel token to another creature you control.

If the ability causes two Rebel tokens to be created (due to an effect such as that of Mondrak, Glory Dominus), the Equipment becomes attached to only one of them.