Create an athlete sponsorship document

Im a full time track and field athlete training for Commonwealth Games next year. I am looking to engage some financial sponsors to fund my campaign. I am fully self funded and work part time to assist in covering my expenses, I am hoping to find sponsorship so that I can focus more on my training leading in to the games. As such I need a sponsorship proposal put together that I can take to potential sponsors. Any advice on approaching sponsors, who to approach and how would be a bonus. I have one potential sponsor in the pipeline who has requested a proposal including an outline of training/competition expenses over the coming year. The document would also need to outline me (background etc), my achievements to date and goals for now and the future etc. Obviously this is information which i would need to input myself (if the doc were a template for example) or provide for the freelancer to include. I have no experience in putting together a sponsorship proposal so direction on content is important. I am happy for the document to be a template which I input the relevant info into myself, or alternatively I can work with the freelancer for a complete product. I want a professional product but something that doest look over the top as I am self-managed ad will be approaching potential sponsors myself- as such I believe the proposal needs to be modest but appealing.