I have faced this exact issue for a client. We have discussed two approaches...
1. Have them find a very specific target market and build a site, SEO, content, pay to click, etc. around getting people for that very specific target market to the site. In other words be the "the" mortgage broker for that specific target market.
2. Focus on the local market and use things like Google Places or getlisted.org and other local directories to list their site. I think with this strategy you will still have better luck focusing on a target market and using a content and advertising strategy to get people from that target market into the site.
The problem with this industry is there are a million of them out there and the really big guys like Quicken Loans and others are tough to beat out on pay to click or with SEO so the target market is a good way to try and maneuver around this and possibly rise above the crowd and differentiate yourself.