I Transmigrated to Great Qian and Have an Interest System

The protagonist's soul travels into an alternate ancient world, where he becomes a low-ranking soldier in the Great Qian Dynasty. He also obtains an Interest System, which gives him an initial principal of 1,000 yuan that grows by one percent daily through compound interest. The System shop sells food and water, but he has to pay for them with System funds. The shop can be upgraded, but that costs money too.