An Introduction to Geocaching
The GPS Receiver
The only thing you really need to find geocaches is some form of GPS receiver. While this isn't strictly true, as a rule (I have found several caches without the aid of a GPS receiver) but for the sake of argument, this is one piece of equipment you really can't do without.
Some geocachers are obsessive about their GPS receivers; always purchasing the newest equipment as soon as it hits the store shelves. Other cachers are largely indifferent, content to use second-hand GPS receivers ten years out of date. There are upsides and downsides to both of course; new GPSs, while offering the latest features and sporting a wide array of modern technology are getting more and more expensive. Old GPS receivers to many are like a well-worn glove: they do the job, and do it well, without any fancy features. Of course, the repeated hits to the wallet from buying the newest technology can pay off for those who are really enthusiastic about the sport (an example of this would be incorporating newer technology, such as the ability to use non-GPS satellites for navigation), but in no way should you (assuming that you are a novice geocacher interested in this sport) construe this as an endorsement for buying the latest and greatest.
If you are new to geocaching and you are on a budget, it is advisable to track down (preferably borrow) a GPS receiver to get started. Many new cachers are very enthusiastic about their newfound sport and rush out and purchase an expensive device without comprehending the necessary or desired features. Take your time in deciding which GPS receiver to purchase - you'll probably have it for a long time, so you don't want to be stuck with a unit that is inferior in any way, or a unit that you overspent on and becomes obsolete without you utilizing all the features. If possible, try and borrow a device so you can find some geocaches and get to know which features you need and which ones you don't.
The simple fact is that most any GPS receiver will suffice to find a geocache; even a unit that's extremely old will probably work just fine. eBay is a good option for finding a used unit without costing a lot. After all, it's better to spend a small amount of money with the expectation that perhaps someday in the future you will upgrade to a more advanced unit - but, perhaps you will decide that you don't need to.