Take a look at the charts in the article, A Brief Letter to Start-up CEO’s, CPO’s and Founders. I like how it shows that no matter what you do to your on-page content, the easy part, search engines put a huge emphasis (roughly 75% of total ranking by their estimates) on links from other sites, the hard part. Three factors make up the value of the links, the raw link popularity (PageRank), trust and authority of the site, and having good anchor text from diverse sources.
So how do you get these links? Think about people you work with in your real estate business. Are there lenders, inspectors, relocation companies, networking groups, government offices, university departments, or other businesses you work with on a regular basis? Would they be willing to link to your site? Maybe they would if you have excellent educational content for potential buyers and sellers. If these groups regularly send business your way, why not ask them to link to your website too?