Hi, I'm hoping for advice and opinions concerning the question as to whether it is advisable to purchase a used iMac (20 inch early 2008) running on OS X El Capitan Version 10.11.6. The Mac is coming from a school I work at, Processor 2.4Ghz Intel Core 2 Duo, 4GB 800 MHz, DDR2 SDRAM, Graphics ATI Radeon HD 2400 XT 128MB. My concern is that apparently from Fall 2018, security updates will not be available. Also, I intend to use Adobe Premiere and Photoshop (I have an online licence), and am concerned the latest version may not run on OSX El Cap Version 10.11.6, or certainly not be upgradable for very long. The sale price without a keyboard or mouse is £150. Any and all thoughts, advice, comments very welcome. Many thanks.