I made a new account another day becasue I was bored, I decided to start with a Doctor. And I train her up to lvl 8 now. When I sell my service for one night with nourished hunger state, the next morning it went all the way to starving. So I noticed that doctors, chiefs and Engineers only do services when nourished, fine and hungry. They lose 8% of their hunger state each service hired. So that means you have to keep your character nourished every time when you want to earn money by doing services.