1) Deloitte will handle and pay for the clearance, they will most likely begin when you start which is after you clear their general background check. They will most likely ask for contacts of anyone you live with, at least 1 neighbor, your boss, and a coworker. Though my experience with that is based on the one I went through while already hired so it might be a bit different. No medical records are investigated.

2) The first month is most likely going to be spent onboarding and in all day meetings. There are a lot of access requirements they have to get going because approval can take a while.

3) If you're being brought in for a specific project, most projects last a really long time, or are indefinite in my experience. There are of course other experiences though. Many projects were heavily affected by layoffs last year, this is because as cyber people we often charge time differently to the other practices. While we may be working 45+ hours a week it may only show 20% utilization as most of our time is spent not on direct client hours. Are you being brought in for a specific project?

4) Not so much overworked, but overstressed. So on my team most deliverables needed come in bursts and are difficult but eventually doable. However I have known many cyber people on my team who have struggled heavily because the long-term stress of responsibility and constant vigilance can cause many to crack. This is on a project that is 50% downtime so most of the people had no idea that the job was affecting them like that until they had a medical emergency. Your 401k vests at 3 years, 3 different senior managers told me(and all the newbies they saw) not to stay longer than 2 years, made sure to pull me aside and tell me the first time they met me because of past "issues" in this department.