Some people might be worried about changing the time on the game incase their family suffer from depression or become extremely weak so here's an easy tip to help you out.
As the game works in real time, your characters normally sleep during the night and not earn very much money during it. Right? All you have to do is change the day/night button over when you go to sleep so your family work all night and then change it back when you wake up so they can work all day too. You might want to try it every other day so your family get enough sleep.