What are the pre-requisites? Is an educational background mandated by the NCAA or the university? I ask this because Sensabaugh has withdrawn from the university and I was hoping he would work with defensive backs.

That sucks that we withdrew. He made the news this year with a story about him coming back to school to finish his degree

According to the job posting on jobs.etsu.edu these are the minimum requirements:
Bachelor's degree, football coaching experience, and basic computer skills. Final job offer contingent upon complete background check and receipt of official transcripts. No prior involvement with NCAA major rules violations.

The NCAA does not require a degree to coach. Each institution sets their own requirements. It's generally a requirement at most schools. Basically, it's difficult for a coach to ask kids to graduate and advocate for a college degree when they don't have one themselves. It looks bad for the university as well to hire individuals to prominent roles who don't have a basic college degree. It's my understanding that Mister encountered this when he tried to get into college coaching initially. That was why he came back and finished his degree.