RX 580 I like more but I don't recommend you to buy these GPU second hand. You don't know how they worked in the mining business. They can be overheated. They certainly require replacement of thermal paste. On this equipment there is no guarantee. The payback period of these GPU 7-10 months. It seems to me that you can not pay back. It is better to buy a new one.
I will be getting the receipt for the cards I buy, and here in Norway there is a reclamation rule that basically gives you the right to return the product in cases of failure within 5 years of purchase, so I think it's all good. So you think its gonna take me that long to pay these cards back? I am mining with NiceHash approx $4/day at equihash/lyra. With 6 cards I should be making atleast $20 a day, and I'm taking into consideration that these coins will very likely increase in value over time, so it's not gonna take that long as far as I can tell. $600/month - 20kwh/day which is about $60/month. 3 months I should've made my money back considering I get the 1070's at around $300-350 each, and this is even if the coins that I mine don't rise in value. Or is there something I'm forgetting here? :p
These numbers seems to be fluctiating quite a bit

Now suddenly I'm gaining $8/day
https://i.gyazo.com/3f29b2c79ead59bd732c846b27513bab.png