To tempt the the Sorcerer even more I offered him Hellfire, he has to spend a fate point to use it but it gives a bonus +3 stress to any hit and +3 stress even if the roll fails.
The book actually has spellfire specced out as a type of sponsored magic. Might want to look it up. I think that approach will work better than what you're rolling with, especially since it sounds like you're 'forcing' his character to change to use it. Let sponsored debt cover that.
-My friend is in an ally fighting an ogre and he wants to find an iron chain. I say, "make a declaration and declare their is, "junk everywhere" so he can invoke it and have tons of trash everywhere. He wants to roll an investigation to see if their is Junk instead. If he did that it would still be a Declaration because he is using the applicable skill? AKA Investigation. The question is, Does he have to take an action to just look and see that their is junk? Does he have to create the aspect, "junk everywhere" just to make it true or if he rolls the investigation instead of using a deceleration he can find junk without using an aspect, He's human and doesn't want to spend the fate points since he hates taking them from me. I'm trying to use my brain but it's on the brink of understanding but just can't get over the last hump.
There are multiple ways to make declarations. Sound like your friend is trying to use one, you want him to use another.
Approach number one is to take an aspect (scene aspect, character aspect, whatever), spend a FP, and declare, "Well, this scene is [Full of Junk], so I find a steel chain lying around!". This type of declaration is pretty open, based on available aspects, and easy to do. It just happens, adding a new [Steel Chain] aspect to the scene (or character).
Approach number two is to use a skill to make a declaration with a skill. The skill needs to be relevant to the discussion -- no using conviction to declare a [Impending Rainstorm], no using alertness to declare [They Don't Want to Be Here]. The rules regarding the difficulty for this type of declaration can be found on page 313. Basically, the more interesting the declaration, the easier it is to do. [Idiot Plumber Left The Power On] might not sound that interesting a declaration. But if you're in a fight, in a flooded basement, and the idiot plumber in question was an NPC who has a 'rep' with the party... That could easily become an alertness roll of 0 declaration. The party laughs as the idiot's idiocy is confirmed, making the declaration itself interesting (or funny). It has interesting consequences if acted on, and (to me at least) it just screams some interesting plot points as both players and enemies scramble to get out of the increasingly electrified water, while shoving their opponent in. A simple [Boxes piled everywhere] aspect in an attic isn't that interesting, doesn't really have interesting consequences, but does suggest a vaguely interesting plan of action. I'd probably give it a difficulty roll of 5 on alertness.
To get back to your original question -- investigation is too active of a skill to make this type of declaration with. If you had time to thoroughly search, sure I'd allow it's use over alertness. But just noticing something is an alertness roll.
-The plus and minuses on the abilities and spells. For example, Inhuman strength cost -2 refresh to take as an ability. Say the PC has 3 total refresh, he can afford Inhuman strength and only that because if he drops below 1 refresh he is pretty much dead. If he had 4 refresh he could take inhuman strength and something else that costs -1. These numbers do not represent any type of cost outside of of choosing them to begin with? They don't say, cost -2 refresh to use? then you can't use it again or else you drop your refresh below 1 and you are knocked or dead?
Think of it this way. You have X many points (refresh) to buy abilities with. Once you buy an ability, it's yours -- permanently. The only rule is you can't spend all your points (refresh) up front. You can use your ability as much as you choose, subject to the rules of the ability. (Some powers / stunts require you to spend a FP to do things, limit you to once a session, etc etc).
In addition, when there is a compelling storyline reason to do so, you can 'temporarily' buy new powers. You pay the cost in FP, and gain them for the duration of the scene or session as determined by the GM. I think the book says scene, but I'd probably allow them to continue longer based on the story given reason for the upgrade -- if you 'bought' help from a faerie court on a dangerous mission, the help probably sticks around until your done with the mission. As does the debt. This does (could, at least) 'temporarily' reduce your refresh to zero or lower, which would normally be NPChood. Dangerous, that. This probably doesn't happen that often. One good example is when Harry picks up Summer Fire (AKA sponsored Summer Magic, which hurts winter faeries) from absorbing Lilly's butterfly in Proven Guilty. I'd argue that picking it up gives him a scene's worth of recuperation (hello cleared mental stress boxes, I missed you!) as well as even more firepower.