Zero interest loans is a possible practice but not negative interest loans ! They are ridiculous. It occured only once in the past (it was in japan) and for a very short period of time and at a negative rate which was very close to zero (it was "minus peanuts", which is equal to zero). This was a side effect of stupid regulatory constraints in order to avoid entities to hold loads of cash. This behavior was sanctioned by the Japanese central bank. After a couple of months, everything went back to normal i.e. the positive interest rates territory.
Please do NOT implement the possibility to have negative interest rates. This is an absolutely ridiculous idea.
On the contrary zero-rate loans are OK. But it seems that you are not really aware of the mechanisms behind fixation of levels of interest rates.
Just as a reminder: when economy tends to grow too fast , the central bank has the option to increase its own interest rates and try to influence the market. This is to limit inflationary tendencies by reducing possibility of money creation through lendings.
On the contrary, when the economy is slowing down (recession, depression) the central bank has tendencies to decrease its interest rates (and possibly to zero%) to stimulate loans and money creation and try to stimulate the economy.
But I really don't know how all this translates in a credible way into the 19th century monetary system in order to keep a realistic system!
So please, don't destroy the game by introducing science-fiction features like negative interest rates where you get paid to borrow money which simply doesn't exist in real life. If it existed, we would know it and simply getting richer by borrowing an infinite amount of money.
