Can't afford Photoshop? Consider instead the open-source alternative the GIMP (GNU Image Manipulation Program), available cost-free for Windows, Linux, and MacOS. Like Photoshop, GIMP allows users to manipulate and save images in a variety of formats, including GIMP's native file format, XFC -- great for saving images that you plan on working on later.
If you're already familiar with Photoshop, you should have no trouble making the switch to the GIMP. The menu and toolbar designs of the GIMP will look more than a little familiar. If you're new to image-editing -- or if you're hoping to upgrade your skills -- the main GIMP website links to a number of excellent tutorials, all much more readable and informative than anything I've ever used for Photoshop.