If you'd like to keep playing here's what is probably going on. You need to have one house for each workin building. Make sure the work-building is within the home's radius. Your farms alone will not provide food to your homes...just produce it. You need to either build a granary or bakery and butcher's shop in order to provide food. Fires will start for two basic reasons: 1 your home/building is unemployed or 2 they don't have food, entertainment or religion. Usually Food is the most important element. With Plebs all you need is a granary to reach 30 satisfaction with food. Disease will occur if there are no fountains or herbalists nearby. Saddly, if a fire does start your best bet is to demolish the building and rebuild it. Fires are a wakeup call that something is not up to par in that area of the city...either unemployment which causes fires spontaneously, or lack of some service which leads to crime=fire.
Hopefully this helps you out, if you still have the game I would give it a shot. Once you get used to how things work it's pretty simple, and most of these problems disappear alltogether.