Could you explain why difficulty would increase after 2 weeks? Is that every two weeks that the difficulty would increase? Until when? Until I start making zero profit and go into negative?
Yes, it will keep going up until you start paying more for the power bill than you earn.
See, this rather simple math, your profit is decided mainly by two factors, price, and difficulty.
You want higher prices and lower difficulty for more profit, the opposite = less profit and potentially a loss.
The facts are, the price can go both ways, the difficulty only goes up, of course, it doesn't go up in a straight line, but if you google "bitcoin difficulty chart" you will understand that difficulty tends to go up a lot more often than the opposite direction, as a result, at one point into the future, your mining gear will become obsolete, that heavily depends on your power rate, someone who pays 5 cents can mine a lot longer with the same mining gear than someone who pays 10 cents, so with 12 cents kWh, you are going to be forced to shut down a lot faster than many other miners.
The above doesn't mean you won't be able to ROI and make some profit on top of that before having to shut down your gears, it just means your chances are a lot lower than those who have free power or pay only 4 cents, and given that mining is essentially a competition between miners, you might want to avoid getting into a battle knowing that the other opponents have more chances than you do.
