(at around 36 mins) When Tricia and Callie go looking at apartments around the midpoint of the film, the first empty apartment they visit was actually the very apartment that director Mike Flanagan lived in (with four other people) when he moved to Los Angeles in 2003. It was a complete coincidence; the unit just happened to be vacant, and Flanagan had no idea they'd be filming there until they arrived on location that morning.
Funded in part by over 300 donors on the crowd-funding website Kickstarter.com. The filmmakers set out to raise $15,000 over the course of their 30 day pledge drive, and ended up raising $25,000 (more than one third of their final budget).
First appearance of mirror from Oculus (2013) and Oculus: Chapter 3 - The Man with the Plan (2006) is at 23:18.