New future outlook based on new info.
Year 1 - 1170 DMD a month * 12 = 14040 DMD (50% interest on all mature coins +7020DMD) = 21060DMD
Year 2 - 21060 DMD + 14040 = 35100 DMD (50% interest on all mature coins + 14040) = 49140 DMD
Year 3 - 49140 DMD + 14040 = 63180 DMD (25% interest on all mature coins + 14040) = 77220 DMD
Year 4 - 77220 DMD + 14040 = 91260 DMD ( 25% interest on all mature coins + 21060) = 112320 DMD
Year 5 - 112320 DMD + 14040 = 126360 DMD (25% interest on all mature coins + 29835) = 142155 DMD
142155 DMD =25,587.90 at todays going rate. Keep in mind this is with my modest 2.4 ths aggregate power converted with fees on nicehash. Still a profitable venture and I stick to my original statement that you'll be hard pressed to find a better investment anywhere for such a short term. The us stock market avg is around 9%. The best savings accounts sit around .06%

In my country that solar setup would be crazy: I would get much more money by attaching it to the power network.