Consider including the fees you will pay to your factoring company. These companies will likely charge higher rates for receivables from individuals and high risk clients. Fees can vary greatly so shop around. Be sure to ask questions and understand the fees you'll be assessed if your clients do not pay within the agreed upon terms and become over due.

As an alternative, consider minimizing your receivables by accepting credit cards so you get paid now instead of later. You client can still pay the credit card company later, so the convenience is comparable for them. You could also partner with a financing company, to finance your fees for your clients, and then it is the finance company's responsibility to collect.

What should I say in my business proposal?

Putting together a proposal is about connecting ideas with people and capital. The proposal should pitch your idea to a potential investor from all three areas:

The Idea- why it is great, and how it will be executed.

The People- who is involved, why they are the best people to have, why an investor would back this team.

The Money- how the investors will make a return.

A great book on this is called Keys to the Vault by Keith Cunningham.