shared data location

Hi -

A couple of things here to address:

1) The data location depends on how you are using the tool.   If you create a report in Import Mode, then the data will be extracted from the original data source, and will reside in the Power BI report itself.  If you create a report using DirectQuery mode, then Power BI effectively just acts as a "pass thru", and all the data remains in the original data source.  

When you upload a report created in Import mode, the data AND the report are then stored in the MS cloud inside the Power BI Service.  In order to automatically refresh the data in that report, you have to set up an On-Premises Gateway in order to connect that original data source to the Power BI Service.  This is even more critical in the case of a DirectQuery report, since you will not be able to access the data without a Gateway in place (with some exceptions that I'll avoid mentioning for now)    

2) Sharing with clients OUTSIDE your organization is somewhat supported, but it is definitely NOT the primary use case for Power BI.   That path gets complicated very quickly, and if external sharing is your prime goal, you will need to look very closely into what Power BI will support.

In sum, the ideal situation you describe is NOT a 100% fit for the functionality provided by Power BI.  Factors like the data source platform, size of data footprint, and number of creators will impact how you might implement.

Hope this helps!