The great thing about real estate related .com's is that you can always bring up the, "what if you got one sale from the name" argument....Think about it - the avg home in America is about 215,000k...Beach homes are usually much more expensive. A 6% commission on a 215k sale is $12,900...there would be a 50/50 split so the agent would make $6,450 (not including splits with their broker) But the fact is that ONE sale in the entire lifetime of the domain name would pay for the purchase of the name hundreds of times over (if sold at 200). If an agent is looking to brand their entire business with that name, it's WOEFULLY undervalued at $200.
You could even allow them to lease the name and pay you for any lead you aquire or a larger % of any sale that is first aggregated through use of the site - I have experience on a National level with that if you're interested (pm me). Don't worry - my advice is free.