|Impossible to say without seeing the building. A lot depends on the construction of the building, wood, stone or brick. Are there steel beams in the building. How thick are the walls and how spread out are the apartments. Although the theoretical maximum range of wi-fi is 100 meters, that is under ideal conditions. Inside a building the maximum range is often a few tens of meters.|
80 people all trying to use the same Internet connection simultaneously is going to cause congestion. Is the Manager and Social workers going to be happy with that.
It could run into many hundreds of dollars. The only effective way to find out is to hire a professional to do a survey and come up with an estimate. What you are proposing is not something that someone with little technical knowledge should be undertaking without some expert assistance on hand otherwise you could end up spending a lot of money and achieving very little.
Sorry to sound a bit pessimistic but there is a world of difference in connecting 80 apartments in an apartments block and a few computers in the home via wi-fi.