You want to get in front of the most people right, so where would that be online?
Its all about RELEVANT traffic, and not just traffic IMO.
Meaning, if someone is searching for how to make inflatable blow up dolls - thats not exactly your ideal target audience for real estate.
As far as advertising goes, you can either:
1. Own your web presence.This can be done either through Pay Per Click (PPC) ads for specific keyword searches, or through investing in your own web presence on a website or blog. They all drive traffic to YOUR website, and establish YOUR website as the authority in your market.
2. "Rent" your web presence on other sites that you don't own.The most obvious choice right out of the gate would probably be Realtor.com enhanced listings as just one example. The downside of course is - you are establishing the OTHER sites as the authority for your market in the eyes of the consumer. (Which can ultimately lead to higher fees that they can charge down the road as they become more and more dominant for your market.)