This gig is a really special one to beat your competitors on search engine rankings.
First, you need to know the strength of your competitors. In terms of SEO, you need to know their backlink sources. By knowing this information, you can either replicate their backlinks or may create something better.
Second, you need to know the keywords they are ranking for. So, you can target and use those keywords in your content. It saves a hell of a lot of time.
What are you going to get in this gig?