In reply to Philip:
Nice little machines as they are fairly easy to work on - but be careful with the IR sensor though if putting a new SSD in, as it can break if you are as cack-handed as me. Not a major issue but it stuffed the 'on' light so confuses the Mrs.
As they are the last model to have relatively easy access to RAM and HDD they keep a high price. Add your own RAM to keep the cost down. I have the i7 version here happily running Windows10 and OS X El Cap.
If the previous user was stupid enough to send on his data then remove drive, wipe, and reinstall - you will want an SSD for the OS and a terabyte HDD for the data.
Neither Office nor Adobe will be tied to an Apple ID but if putting a new HDD in they might want the serial reinstalling, so make sure you have the keys to any software that might need reinstalling.
cheers
b