Items that cast spells and Neutral Hostile abilities

2 dumb questions:

1) If I make an item and give it a unit spell ability, such as cripple, then when the hero tries to use it it sucks out his mana, or wont work at all if his mana isnt high enough. Is there a way to get around this?

2) Whats the difference between regular abilities and neutral-hostile abilities? If I give the computer players (or neutral-hostiles) control of spell casting units such as priests or banshees, should I change their abilities to neutral-hostile ones?

You asked about what happens if you add spells to items and I've been wondering about this my self. I decided to test it and try to fix it and found out that you can not make an item with a spell ability not use mana. There is one way around it though, you have to make a trigger that says that when the item is being used it adds the amount of mana it required to cast the spell back to your hero. Unfortunantly this does not fix the problem where your mana is to low to begin with. Also, I am not sure if the number of charges on the item affects this too.

In response to your second question, regular abilities are set to go to the position they normally preside in and require you to research their upgrades. Neutral Hostile on the other hand resides in a different slot and never has to be researched. Using different variations of these two types of abilities, you can stop the overlaping of skills sometimes.

So I only need to use neutral hostile spells if they require research, eh? If im not using an AI and I just use triggers to order them to attack-move, will they use their spells or just attack?