Sound
Here are some ideas to help you with the sound part of your haunt.
Go to garage sales or goodwill stores and find a cheap CD player(s) and speakers. You can also look at Walmart or Kmart too.
If you are just having spooky music or sound effects not coordinating with any particular scene you could just have one source of music playing loudly so you can hear it throughout your haunt. But if you want sound pertaining to just one scene you can use a separate player and speakers having a cd with the certain music or sounds you want for that scene.
You can use a program called Audacity this is A free, open source software for recording and editing sounds. I use this program to make cd's for my scenes. You can record sounds, or open saved (copyright free) sound files from the internet and combine, change speed and pitch, add echo and many other effects to make a very unique sound combination or music track. You can also make tracks go back and forth between the left and right speakers (great for whispers in a hallway scene)!
There are sites on the internet that do offer copyright free tracks or sound recordings for your use.