I have been asked several times, generally by tradesmen, whether they can buy the test equipment and test their own tools and leads. This is generally after they have been told that you do not need a qualification to test and tag, rather be deemed competent.
Buying the test equipment is easy - you can pay anything from $1000 for second hand equipment upwards. The old story of you get what you pay for is very relevant here. The test equipment must be able to complete all the test requirements - of which there are several, depending on what is being tested. There is equipment available that completes all tests in one unit - and these units often have a printer attached so the tags can be printed out after testing.
How to use the equipment? Teaching yourself is not an option, nor is getting your mate who is an electrician to show you how to use it. If you need this sort of guidance, then this option is not for you. There are courses available - starting from the basics of testing through to becoming licensed as an Electrical Service Technician.
But the most relevant issue is competency. The NZ standard regarding testing and tagging AS/NZS3760-2010 1.4.4 states a competent person is one who the responsible person ensures has the necessary practical and theoretical skills, acquired through training, qualification, experience or a combination of these, to correctly undertake the required tasks.
If you test and tag, the best way to look at competency is to ask yourself "If there was an accident as a result of my work or after I tested an appliance, how could I prove my competency in a Court of Law?" A combination of training, qualification and experience is generally the only way to be able to prove competency.
So unless you are prepared to spend money on equipment and training and then spend considerable time gaining experience using the equipment, the best advice is to let qualified people test and tag.