i am planning to develop a web application that is accessible from the internet.
i want to have a web based application for apartment rent management system.
so the application will register each apartment and the tenants within the apartment.
let say Apartment Abc has 12 floors and 20 rooms on each floor.
then the apartment ABC will be registered in the system along with its tenants,rooms, floors
Apartment xyz has 8 floors and 15 rooms on each floor. xyx's rooms,floors, tenant details will be registered.
apartment def has 5 floors and 20 rooms on each floor, def's rooms,floors,tenant details will be registered on the system.

each apartment will have its own login system, so that when apartment ABC logged in..only his own apartment details will manage(floors,rooms,tenants,payments...)
then number of apartment could be any number...
so how to handle this kind of application, if i should use a single database for each new company(apartment) how can i do that? or if there is a mechansim to handle this kind of application with single database.. let me know please?