With taxes the way they are in DCity, the biggest way I earn these days is from the tax refunds and my biggest tax refund comes from students. I used to get them pretty frequently at one point before the changes were made and then it remained stagnant.
A couple of days ago, my chance of getting a new citizen was at 2% so I am trying to increase this as much as possible. One way is to increase the popularity of the city. That means getting more ice cream shops, music shops and the like.
I have also created some bids on ice cream shops and if anyone wants to sell theirs then I hope they would consider my bids. The DCity market is really interesting and there are numerous opportunities with the spread between the bids and asks.