Hi Oliver,
AdHoc reports are free. The note is intended to have developers make
sure they have not used up all their available units within their monthly
budget (any free units + paid units from budget). You need to have at
least 1 unit (paid or free) available to run reports, but the report
I'd been under the impression that adhoc reports are free until I came
across a comment on this page:
https://developers.google.com/adwords/api/docs/guides/reporting
it says:
*Note:* Although AdHoc Reports operations do not incur monetary costs, they
still count against your monthly operations
