I am quite new in this mining "business" and had a conversation with a friend some days ago. He is living in a shared flat where they don't pay the electricity and so he is mining with his own PC...he says, that he is not going to be rich with this, but he gets at least something. But, when paying the electricity (as the most of us do), when is mining profitable if one has a certain hashrate? I mean, its not easy to calculate because the difficulty also rises with the time. In the end, all this effort could lead just to a loss of money.