advice on making a proposal

I have been asked to make a proposal for my company and need a little advice from anyone that has experience in making up proposals in the past. I work for a Bathroom and Kitchen company, we have several showrooms throughout the province and get a lot of business driven in by Interior Designers. What I want to do is start a network of commission based sales consultants whos job would be to actively seek out Designers and explain our process whereas the Designers get 10% rebate of each sale. i.e for each client they send in or accompany in to our showroom they get 10% of the purchase price of their customer. We need to pay our commission sales reps a fee, a finders fee which I,m thinking will be ongoing for each sale their designer earns. I have to work out some sort of percentage for which we can afford to pay them and also how do I write this up as a proposal in order for it to look professional to my Director. In otherwards I dont want to to look like an idiot. Any help would be appreciated. Thank you.