Write the script then put it on the net or share it on here. I'm sure you could get it crowdfunded in bitcoins if it was good enough and people liked it. I'm also not sure if movie companies even listen to 'pitches' anymore and if they do it'll be incredibly difficult to get one, but if you've got a great script it'll probably find its way to them eventually.
I was thinking a low budget one would. I am not looking to get a meeting with warner brothers company unless they want to meet but yeah just a small company could do this easily just thinking about all the different sets. I have no clue what actors are paid or any movie work is paid really.
Maybe, but I think you'll need more than just an idea. What else have you got? I'd still write the script first. There's websites where you can read movie scripts to help you get a gist of what's needed. If you put it on the net and it's good, people will pass it around and it'll get noticed. I think it'd have to be pretty unique or have something new for a horror though. They've been done to death.
