For mine and my brother's horror film, which we began shooting a few years ago now (details provided on the 'indie' board), we needed a large school building.

My brother Alix was attending college at the time and thought that his building, which was huge, and run-down and bordering on being derelict, would make the perfect location, so he called the dean of the school and set up a meeting.

Basically, we went in and told him how much we loved the building, and managed to negotiate use of the building after-hours, free of charge, so long as we paid for a security guard to be present at all times (approximately $3500 in total), kept the locations clean, and waived the right to sue them if anybody was injured.

Thankfully, the lack of liability insurance, which can kill your chances of making a low-budget film because it's so damn expensive, was thankfully never an issue, despite the constant running up and down stairs and occasional knife- and axe-weilding.