Pay Per Click
Pay per Click does not mix well with real estate websites. The reason is small budgets and technical expertise to properly track the campaign. And step one in this tracking process is measurement. And the best way to measure is by creating landing pages. Which also will help in conversions.
The reason you want landing pages is because you want to be able to track that traffic coming from the ad, to the page. Then you can play with your ad copy and your page copy for best results. Eventually establishing a control.
Most agents and brokers are limited by time, money and expertise to properly do this testing and building.
Well, there is something else to consider that may make it easier to track your Pay per Click or banner ad numbers.
Unique Phone numbers. By making your visitors response a phone call into a unique number, you may be able to tell what page, and or what copy is working.
A company that has emerged offering you the ability to do this is http://www.mongoosemetrics.com/. I have no idea if they are any good. I only offer you this as a possibility as I have not tried them out. I am sure there must be others out there.