If you can afford $30 per month ($1 per day education for Photoshop) I suggest first start by searching for a good used Photoshop Manual/Teaching Guide on ebay or an online used book store like Amazon.com
Most modern day computers these days are plenty fast enough for Photoshop editing. If you have a photo scanner or digital camera, that’s a plus! Each day, promise yourself to learn one command or series of commands. That mixed with a great textbook, you can teach yourself Photoshop at any age. Learning Photoshop before entering college or Photography school is a plus to the extent of your computer skills.