There are a number of prerequisites to get started. You should have a Mac or PC with enough resources to install and run Unity. Details of the current system requirements for Unity can be found on their website (https://unity3d.com/unity/system-requirements), including the supported operating system version, the graphics card or built-in GPU, sufficient disk space, and necessary RAM memory.
For AR development, it is also recommended that you have a webcam attached to your PC for testing your projects within the Unity editor, even if the PC is not the target platform for your app, and a color printer for printing hard copies of target images.
There may be additional minimum requirements for your development system dictated by ...