As I have not tried to calculate the profitability of farms. Payback less than a year did not work in any way. I think this year you should not even think about mining. Unless outbid somebody farm (they should be cheap) and leave it until 2019.
I can ROI in 8-9 months right now even if I sold my mined crypto right away. I don't have to do that due to my personal situation so sometimes, even in a bear market, you can ROI fairly fast. You really just have to think outside of the box and mine other things than what is on whattomine. If you see it there so does everyone else.