The fact is that you don't have to have a ton of expensive equipment to conduct an investigation. The main ingredient is the first one on the list, and you can always add to your collection of tools as you go along. Starting out with just a disposable camera will work fine, but make sure you have someone else along, too, not only for safety, but to verify that any evidence you may obtain or experiences you may have are legit.

COMMON SENSE -- It's free, costs nothing to use, and is highly recommended to be used in any investigation! ;)

EMF Meter -- There are many different types of electromagnetic frequency meters on the market, from inexpensive ones to high dollar models.

These meters measure the various electromagnetic frequencies that exist in an area. The readings will vary, and can be influenced by many things, from faulty outlets to microwave ovens.

From all the investigations that have been done, it is believed that a true paranormal event typically affects the EMF fields in the area where it takes place.

Compass -- While an EMF meter is overall better in getting a more detailed reading of EM activity in an area, a good compass can do the job for a lot less money.  The key is making sure it's not a cheap version that has the needle hanging up. The needle should be free swinging, and if you get into an active area, you just may see that needle swinging away from true north!

Digital Voice Recorders, Cassette Tape Recorders -- These are used to try and capture any anomalous voices or sounds during an investigation, known as EVP's or electronic voice phenomenon. Some prefer to use tapes, others use digital, while still others use both.

The digital models have come to be preferred due to the longevity of time they can record, as well as the ease of uploading the recordings to a computer for more in-depth analysis.

Cameras -- Both digital and film cameras can be used to try and capture anomalous events.  Digital cameras with a pixel rate over 5.1 and with nightshot capabilities are preferable, and the best film speed for regular cameras seem to be 400ASA film. Disposable cameras work fine at that speed as well.

It's important to make sure that there is no camera strap flapping around that might get into the picture and give you a false positive for an anomalous event. Either remove it, or make sure it is secured out of the way.

Video Cameras -- Digital camcorders with night vision are the preferred tool of choice.  There are numerous makes and models in a variety of price ranges, it depends on how much you are willing to spend.

Flashlights -- A good supply of flashlights is recommended. It's a bit difficult to track down a loose power cord without one, or to avoid tripping over that tree stump at the back of the cemetary!  Flashlights are cheap, you can get them in a variety of sizes and strengths, and having several on hand is a good idea. You might also consider having some with a red lense, as that tends to make it easier on your eyes in the dark. It's simple enough to convert one you already have by putting some red cellophane over the lens and holding it in place with a rubber band.

Batteries -- You can never have too many batteries!  Experienced researchers have noted that many times when paranormal activity increases, there is a resulting drain of the batteries in their equipment. The hypothesis is that the spirit trying to manifest itself draws on energy sources nearby to do so, thus draining the batteries. Pretty frustrating to be on the verge of getting a good pic only to have your digital camera's battery die! So whatever equipment you use that requires batteries, make sure you have plenty of replacements for them, just in case.

Walkie Talkies -- Good for keeping in touch with other team members in other areas of the investigation. Again, there are many types in many price ranges, just see what fits your budget the best.

Tripods -- Used to set up a camcorder for passive recording. Make sure it's in a spot that is the least likely to get tripped over, while enabling the camcorder to cover the entrance(s) to an area to discourage anyone trying to falsify results by messing with your camera.

First Aid Kit -- Crap happens, be prepared for it. From bug bites to twisted ankles to cuts from sharp objects, and worse, anything can happen when 'ghost hunting'. First aid kits are inexpensive, and just might come in handy! Here's hoping you never have to use it...

Notepads, Pens, Pencils -- Just to write down any impressions you have, temperatures and changes in temps, etc.

Cell Phone -- Keep it off during the investigation, but have it handy in case you need to dial 911.  Hey, don't laugh, it could happen!!!

A Sense Of Humor -- priceless! Not that anyone should act like an idiot, but don't take ourselves TOO seriously. :)

There are other really expensive pieces of equipment that I'm not listing here, as they are so cost prohibitive that it would be a rare group who could even afford them.  For now, this list covers most of what the average team of researchers uses in their investigations.