FAQ

Finch requires MCC access to run an Audit report.

Finch can link to a client’s AdWords account by asking the client for their AdWords Customer ID number. We then submit an invitation to the client asking for permission to link to their account.
http://support.google.com/adwords/agency/bin/answer.py?hl=en&answer=7732

Each direct AdWords account can be linked to up to 5 MCCs, so there should normally be room for Finch.
http://adwords.blogspot.com/2011/06/new-my-client-center-feature-provides.html

Occasionally Finch invites the top MCC of a client. It is only possible to have one MCC link to a top account (i.e. another MCC account).

It is not technically possible for a client to invite Finch to access and manage their account.