Sort:  

First things first, it is super fun to play! It is kind of complex by now, I think the best way of learning the basics is to buy some cards and play around with them while simultaneously reading some tutorial. Things get really self-explanatory once you see how buying certain cards affects your city. But you can always ask me if you have specific questions :) I also highly recommend checking the Discord server, people are super helpful over there.
Generally speaking, the return-on-investment is really high in this game. Before the update, the usual rule of thumb was that you could get your expenses back in only 100-200 days, depending on how well you spent them. It is hard to calculate now, because education and creativity can be a fluctuating source of income as well. It takes probably longer now to get your investments back, because of the tax system.

thanks for your reply! I'll check it out one day