Here is a list of some of the basic equipment used on a ghost investigation. All of these items can be found and brought on-line, there are several good websites that sell these items.
Camera . . .
Digital camera, 35mm camera, polariod camera All of these camera's are good choices. Some say that the 35mm and the polariod might be better than a digital camera because it is not as easy to fake a picture.
Vioce Recorder . . .
Digital vioce recorder, old tape recorder. Either one of these will work. A lot of people perfer the digital because it's small and easy to carry and you don't have to buy tapes to use with it.
Flashlight . . .
Any type of flashlight will work. It doesn't have to be fancy. Smaller ones work best because they are easier to carry.
Batteries . . .
Everyone has there preface on batteries. Just make sure you alway have extra. Ghosts have been known to drain them even brand new or freshly recharged one.
EMF . . .
EMF will detect high levels of magnetic fields. If there are high levels of magnetic interference then there could possible be paranormal activity in that area.
Thermometers . . .
There are several differant types and styles out there.