If someone's mental illness is so severe that they cannot work (and that they need to collect social security disability benefits), they may be purchasing the firearm to do self harm or to harm others. I have known many people who are on social security disability for mental health reasons, both personally, and through my work with patients as an RN, and it's not easy to get-you must have a severe mental illness, multiple hospitalizations, and lots of documentation to back up the claim. Further, it's only the ones who don't even have it together enough to manage their own disability check, someone else has to do it for them as their payee. So, no, these folks do not need access to a firearm.