Hiding certain elements from unqualified users
Our product is heavily influenced by local and state laws. Therefore some designs are not relevant to users who live in these unqualified areas. We will broadcast this new feature on the homepage with subtext that conveys some states will be excluded. But my question is, should I maintain the design elements and just make them disabled for these users? Or should I hide it completely since they can't use it anyways?
For content, the simplest solution which would apply in most cases would be to hide content that is unavailable to a particular user. We want to save users frustration, so why give them something to click on only to tell them they can't use it?
The important exception to this rule is when a user is likely to be on the hunt for this specific content. Rather than make them search around and become frustrated by their inability to find what they want, you should tell them early on, in the spot they'd likely be looking, that this content is unavailable to them.
For your case, you might have to ask, are users likely to be looking to add a cosigner on their loan? In this case, I'd assume that yes, there might be users who go into the app with the desire to add a cosigner for various reasons, but you'd have to do user testing to determine if this is actually the case. An elegant solution would be to display a short notice that "the option to add a cosigner is not available in your location," or similar. Since it doesn't take up much space, it doesn't add much for the users who don't need it, and it saves those who do need it a frantic call to the support line!