Here are the things that you will need:
1. A digital camera (preferably a DSLR camera) with a memory card
2. A desktop computer or laptop that has a photo editing software (such as Adobe Photoshop, Adobe Lightroom, Apple Aperture, etc.)
3. Memory card reader to transfer your photos from your camera to your computer
4. Last but not least, some basic skills on how to operate your camera and your computer
The whole process will cost you $0 by assuming you already have a camera, a computer, and a photo-editing program.
For demonstration purpose, this is the list of equipment that I used to make these sets of instructions:
1. A Canon 550D (Rebel T3i in the USA) DSLR camera with SD Memory Card
2. A 2009 Apple MacBook Pro
3. Adobe Photoshop CS5 for Mac
Different cameras or softwares have different interfaces. However, I will try to give the instruction as general as I could. As long as you get the concept, you should be able to do this using different equipment.