In the time you spend trying to get listed in directories, you would be much better off blogging about real estate opportunities and investment tips, this is much more likely to build free flowing incomming links to your site.
You could also visit similar blogs in your category and add comments, which usually allows you to add a link to your own website. If you help others in your community, they will help you. Its kind of like recipricol linking but Google doesn't spank you for it.
.