Ted Kaczynski hasn't been anything other than a domestic terrorist since 1969 when he dropped out of academia at the ripe old age of 27. Sirhan Sirhan didn't have a profession, as far as I can tell he was working at a health food store when he assasinated RFK, and has spent the past 53 years incarcerated for it.

Charles Guiteau had a long career prior to assassinating Garfield, as did Booth before assassinating Lincoln. While both committed assassinations, there was no point in time where you could have hired either to assassinate someone for you, it wasn't either of their professions.