It does not matter at what level your organisation starts, as a One-Man-Operation, a smale Government department or a cooperation with some branches your application will handle quantity growth without further investment.
The applications we develop are multi user and multitenant from the beginning even if running on a single computer at the start.
Moving that application to a server, multiple users can access it at the same time from different client computers which can run OSX or Windows.
An update to a newer version of the application in this client/server constellation is done by simply updating it on the server computer only.
With little effort the application can be extended to be accessible by any web-browser or feed dynamical content to the existing website of the organisation.