@deangelodenis The issue is the data. Each company will have their own domain. The work you do should be within their domain because you will be building reports that will rely on their data sources. They will want to utilize Power BI in its full extent, Apps, workspaces, etc. Your reports should be part of the eco-system.
So in your example, you would have an account in the AA domain (theirs) and in the BB domain (theirs).
If you have a standard template that you re-use, that is fine and up to you, but you would be building the report seperately in each company because you will be using different datasources. Those datasources are tied specifically to those domains and the gateways to refresh the information also part of those environments.
So, my thought is you would build out templates for how you want a report to look and plug in different data sets depending on client. (If they are the same type of report). We do this all the time and actually have examples on our site - https://powerbi.tips/layouts/
Long and short:
You won't be able to create your own domain, ingest and refresh data and share reports with many other companies. You need to work within their environment and develop the solutions within their company domains.
