Free will

[Ignorant]

Are necessity and contingency real properties that a thing has?  I think not.  They are merely descriptors.

Well of course they are descriptors. What are they describing? Whether an event obtains differently according to different possible sets of conditions (contingent) - OR - a particular event obtains in the same way without any relation to any possible set of conditions (necessary). [Edit - addition: So I agree, they aren't properties "had" by a thing]

You can't mount free will on a non-real property.

I'm not sure I've mounted free will on anything (even though I'm not sure what you mean by "mount" exactly). If it exists at all, free-will would be part of a set of conditions which determine a particular action AND the freedom therein would, itself, depend on certain conditions being met.

In short, contingency describes an event, an occurence, etc., considered in itself, as one that obtains according to certain conditions being met (e.g. a tree making fruit). 

Freedom describes specific conditions in an acting subject which, when present, allow for that subject to act freely. [Edit - addition: When absent, the acting subject can act, but it cannot act freely. (e.g. a fruit tree cannot make fruit freely)]

Obviously, if that act is not contingent (i.e. if it does not depend on conditions) then the act cannot be free (which describes a specific set of conditions). No conditions no freedom. If conditions, then maybe freedom, depending on whether or not specific conditions are met.

If contingency is not real, then neither is freedom. If contingency is real, then freedom may or may not be real, and would require different sorts of questions. That is why I care about distinguishing necessity and contingency.