Networks

Hi TR,
I'm about to start a new venture which will design, deploy and support Networks for huge clients in my city. My company has also been shortlisted to submit our proposal for what solution we can provide along with the cost. Since this is my first client, I'm not aware of how to create a Cost estimate. Can someone in this forum help me with this. Can you also let me know what items need to be covered in my cost proposal. As of now, all I'm considering is the manhours my team will put in to deploy the entire network. ANy more suggestions?
Also, I would like to know if Vendors do charge even for submitting their proposed solution to a potential Client? or the proposed solution comes free of cost?
Thanks in advance.