Hi there, thank you for your feedback.
We've invoice consolidation so if the client has more than one product/ services then you can manage the invoice once which you can do under Setting -> Order option -> Consolidation.
Regarding the invoice, you can refer to our documentation here :
https://docs.upmind.com/docs/how-to-configure-invoice-settings
and here for the Paypal: https://docs.upmind.com/docs/how-to-add-paypal-as-a-payment-method
Hope it helps. Thanks