When it comes to paranormal investigating it can be a very expensive depending on the equipment you use. EMF, K-2s and Mel Meters can cost a lot of money. So, it is very important to set a budget for yourself as to what you can spend and on what not too.
I will tell you this that it doesn't take much to do a paranormal investigation. All you need is a watch, pen, paper, digital recorder, a small camera (if necessary), permission and daylight. Yes, I said daylight because spirits are active all the time, but more often at night.
We've done walk through of places we were going to investigate and got EVPs just doing that.
I've heard from other investigators and physic that the best tool you can use that money can't buy is your body because it reacts to the conditions around it.
Always, research the equipment you want to use and whether or not it would be practical for your group to have. There are plenty of videos on YouTube that other investigators have done reviews of and most of them explain how to use the equipment.
Some also offer tips on how to make your own equipment. I'm not very talented in that, but I do try. A another paranormal group called Viper R.I.P. Paranormal publishes how to videos and other helpful information when it comes to investigating the paranormal.
For our team we always hit up Goodwill, Flea Markets, Ebay, Amazon and other places to find our equipment needs. Goodwill sometimes has tripods for sale, suitcases, TVs, VCRs, and DVD players. Flea Markets and Ebay sometimes you do get lucky.
I am working on a series of equipment review videos of what we have. So, once I finished those they will be on the equipment page and on our Youtube.