a reference to employment status sounds to me like an ad hominem attack. If the person isn't employed, then we're being led to believe that their argument is somehow less valid.

In most cases, I'd expect that the same was true of "mental illness", although "mental illness" covers a lot of ground, most of which isn't really relevant to much of anything. To use an appeal based on "mental illness" would seem to me to be an attempt to dismiss someone out of hand rather than to actually address their concerns. Depending on the situation, that might be completely reasonable, and it might not.

In what context were you thinking of these things?

schizophrenia
schizoaffective disorder
bipolar disorder
major depressive disorder(s)
panic disorder
obsessive-compulsive disorder
pervasive develepmental disorders
- aka "autism spectrum disorders
anorexia nervosa
bulimia nervosa