External
'Maintain' is not defined in the SRCA, however its dictionary meaning gives a clear guide to the ambit of the phrase:
2. support (life, a condition, etc.) by work, nourishment, expenditure, etc.
In the context, 'wholly or mainly' should be given the same meaning as wholly or mainly dependent, i.e. the person was maintained by the client to a greater degree than by any other person.