The Client Overview Tab is the best place to get detailed information about a client in terms of:
Basic Info - Like the client's email, physical address, and fiscal details.
Amount Due - How much money they owe you for how many invoices, which is further broken down to the currency of each invoice. The default invoice term is also visible to know exactly when to expect payments.
Unbilled AR - The total sum of all the unbilled time entries and tasks (based on the default company currency), plus open expenses (with their own currencies).
Billed/received - Shows you at a glance the sent and paid invoices by month or a specific timeframe chosen through a click and drag on the date section. You can also check this information based on the currencies you’ve used.
Time worked/project - Or how much time has the whole team registered against the client's projects on a monthly basis.
Pending invoices - A detailed break down of all the invoices that are still open along with their due date, total amount, down payments, and status (sent, viewed, received).
This way, there's no need to create a report in terms of the client's rentability or unpaid invoices as all these details are available at a glance.
NOTE: Only Admins have access to Clients.