I would like my (B2B) clients to register sales orders on the website that would generate invoices for future payments exactly like if my internal sellers would register them. 

But the website requires I set up a payment method. Using wire transfer is not working for me because:

1. It leaves the orders in the quotation mode, which implies that my sellers have to maually confirm them
2. Once the orders are confirmed, they automatically generate a payment, which never occurred in the first place. 

Is there a setting/a module that would allow me to solve it?

Additionnally, is there a way to limit the amouts/quantities ordered on the website?