Advance payment invoicing

I need to setup advance payment invoicing as one of the payment options offered to a customer on checkout. To bemore precise, at this moment I need to offer the customer the following payment methods:

C.O.D.
Advance invoice
PayPal

and eventually Credit Card (eCard) through my bank.

I do not see any way how to enable plain old advance invoicing in e-commerce. It should behave in the same way as C.O.D. but wth the following difference:

In the case of C.O.D. I ship immediately ipon receiving an order

In the case of advance payment invoicing the system autoamtically issues an invoice to the customer and waits for payment. Only after having recived money I take further action.

Customers paying for goods in advance should be given a discount of 10%.