Invoice creation for different cases

Hi,

We have below 3 requirements to create invoices form Order Management, please guide.

1) Create 1 Invoice for 1 Sales Order. Automatic creation of Invoice for Cash Customers.

2) Create 1 Invoice per month, for a customer.

In this case for all the sales order for a customer , just 1 invoice is created.

3) Multiple invoice for 1 sales order.

In this case, if a order has 10 lines, and partial shipment is done, for eg of 5 lines,

then only invoice of those 5 lines should be created.

And after other lines are shipped, the invoice should be created.

These are cases,  which needs to be configured.

Please guide.

Regards,