I bought an iMac from www.tier1online.com because I thought it would be good to learn how to use one and because it was £109 and had a 20 inch screen!
The specification is
Grade Refurb
Type iMac 20″
Processor Intel Core2 Duo E8135 2.66GHz
Resolution 1680×1050
Memory 4GB
Hard Disk 320GB
Operating System Yosemite