Ok, so you're over in Australia. I'm not actually sure what $600 AU dollars translates to in American currency
But here's the thing:
You can get a brand new laptop
http://www.dell.com/au/p/inspiron-11-3162-laptop/pd?ref=PD_Family starting at about $300. You can get a brand new, really good laptop for $550. That means the hardware is modern(vs hardware from a few years ago, you'd be amazed how much can change in just a few years) and a brand new unit is always going to have a better operational lifespan than a refurbished unit.
Think of it this way: the machine id designed with an operational lifespan of about 5 years. Even refurbished, the hardware litterally decays. So if you buy a 2-3 year old refurbished machine, you've only got so much time left on it. It doesn't matter how repairable it is, replacement parts will cost more than you spent on it.
Obviously I'm not telling you how to live your life, but I've bought a loooooot of computers in my life. A lot of new, a lot of used, a lot of refurbs. For the money, new is always better. This is double true for laptops.
Thanks for the feedback.
My considerations are mainly based on this forum.