Use any simple mining calculator i did some calculations below in the pic. Based on the way things are going 28% increase every block (5-7 days) is about right before the newer machines come out. In the beginning it will be good but after you earn about half your investment back the gh/s will become nonexistant keep in mind this is assuming the 28% increase which will most likely rise drastically when these terraminers come out. THis is for 1gh/s and does not even account for the 8% fee this website will charge you. The profitability of actually owning the 1 gh/s miner is mining with it for a while then reselling it and having a nice profit from the amount you mined in a month or so.