Modifying NS to Accomodate Business Process

Hi,

I'm trying to modify the NS procedure for billing to correspond to our business model. We work in the commercial real estate industry and 95% of the time we are paid by a third party, rather than our client. The third party is either a property owner that is either selling or leasing a property. Our client does not get billed for our services.

We have two primary services:
1) Tenant Representation Services - identifying commercial space and lease   negotiation on behalf of the client
2) Acquisition/Disposition Services - buying or selling commercial property on behalf of client

When we provide tenant rep services, we submit RFP's (request for proposals) to Landlords of potential properties. Once these are received, we submit them to our client. Once a property is selected and a lease is signed, we invoice the Landlord of the property, not the client. I want to make sure that our clients do not recieve any invoices/bills/estimates via email. Is there a way to manipulate the NS model to accomodate our business process?