When you say "Resources" what are you referring to - media? sources? citations?
Sources & citations are held within the .FTM file, so they are not shared among trees. Media is another story. Media (pictures, documents) are "Linked" in the .FTM file but the media items themselves are separate files.
By default FTM will put all media in a subfolder of the folder where your tree file is. For example if the tree is called "Smith Family" then in your [Family Tree Maker] folder there will be a file called "Smith Family.ftm", and a subfolder called [Smith Family Media] containing all linked media. However depending on how you have chosen to link the media, it may or may not be moved into that folder - you can tell FTM to link to media in-place, so that multiple trees could link to a single media file. See settings in Tools>Options to see how your trees are set by default, but that actually only shows how new media will be managed - not how existing media is handled.
A safe way to ensure each tree has its own media is to export each tree to a new file. Make sure your defaults are set to organize media in its own folder (sorry I'm on Mac so can't check the exact way that's worded in Tools>Options for FTM2012). Then export all items, making sure you check "Include only items linked to selected individuals" (see link below). Once you've exported to a new file, all media for that file should be in its own Media folder (e.g. the [Smith Family Media] folder noted in my example). http://ftm.custhelp.com/app/answers/detail/a_id/4376