A software vendor has expressed interest in sponsoring my site. They asked me to author a marketing proposal.

Basically, I would run their banner in selected spots, as well as let them send out mailings to my site members who have opted-in.

This in exchange for a set montly fee and a minimum commitment of 6 months.

Has anyone else written such a proposal? How formal do they need to be?

I will draw up invoices and contracts for advertisers. It will include my logo, mailing address, e-mail address, phone number, and fax number. It will also include a detailed listing of exactly what the advertiser will received with an itemized price breakdown. At the bottom, is an area for both the advertiser as well as me to sign.