I, too, recently have been thinking about mining farm. As a diversification. There are people who advise mine ether and zec, but what do you advise?
Only advice that I could give to you and other people, is to stay away from mining for now. Profitability of mining has fallen drastically, also prices of GPU's are too high. You would need large investment for start, and not to mention rising in mining difficulty. So for now you should stay put and observe.