Basically, they will schedule the interview at your house b/c of the sensitivity of the information plus they want to verify where you live and what kind of environment it is. I had asked to go to a popular coffee shop and my investigator pushed to come to my home. Not that I mind, it's just a live with all guys so you can imagine what my house looks like. Strap a deodorant stick to a fan...you have a manly glade plug-in.
You should maybe just need an ID to prove it is really you. And from my experience they just ask for contacts from college, your job, friends, and neighbors.
Weird. They told me that they absolutely could not do it at my house, and instead chose a library nearby. Otherwise, everything was the same as others have said. They did mine before the board because I was initially going down the NUPOC path and that is a higher clearance...I guess.