I'd advise you not to buy it.
You can buy brand new GTX 1660s for ~
$380 AUD. So for your friend's 1060 you'd be paying not far off that amount for something less powerful, with an older architecture (less driver support going forward), and no warranty.
I had a look at
Ebay in Australia for 1060s and there are auctions on there starting as low as $99, with multiple "buy it now" options at $250. And $250 AUD sounds a bit expensive for a 2nd hand GPU too. You can buy brand new RX 580s for ~
$285 AU.
So I'd politely decline and wish him luck on ebay,
If you want a GPU upgrade, get an AMD RX 570 for 210 AUD:
au.pcpartpicker.com
An RX 570 is not too far off a GTX 1060 in performance. Technically in the GPU tier below, in BL3 the performance is relatively close, if you look at
this benchmark from
this PC Gamer article.
That would be a much better deal. Cheaper, similar performance in your favourite game, and unlike your friend's GPU will carry a warranty. You never know when these things might die on you out of the blue