My house didn't have security (in the 80's), but really, we could have. There were some pretty frightening incidents of weirdos and break ins at or near all of the sorority houses on campus. And with some of the houses holding upwards of 100 girls now and NOT being budget housing, it makes complete sense to me to add security.
I can't imagine you will be walking the floors of the house. It is an actual house after all. But I imagine you'll be frequently checking the doors and functioning more as a door man. Maybe making sure the kitchen stays locked after hours
My advice to you, having lived in secure apartment buildings, is know all of the girls by name, know their boyfriends and best friends (subtly of course) BUT don't try to become a friend or boyfriend. Also, when 50+ girls all live together, there is a world of drama that you can't even imagine, particularly at that very special time of the month (and yes, they really do sync up). Stay out of the drama and know the difference between a girl having a meltdown at her boyfriend and abuse. Unfortunately, we did have an abused sister and it would have been great to have an ex-soldier there to kick his arse.
Let us know how it goes! I'm also interested to hear how this will actually work.