The question:  How do these people get their leads?  
http://www.realtygenerator.com/corp.html
Additional clarification detail on what I wish to know - 
(Specifically: what kind of keywords do they use to get their hits?  
How does their lead generating system work? 
Is it worth it to use their services or would it be just as good to set
up my own web site and get the hits directly instead of paying for
their services to provide me with leads?)

This is a free comment.
I just have to wonder:  If Realtygenerator is so web savvy, why don't
clicks on Legal Policy, Privacy Policy, Search or Site Map work?

Perhaps a good place to start is... Google!

Search for "Realty Generator" (with the quotes to have an exact match)
and you'll get roughly 287k results. Of these web sites, you'll see
many of them cater to local real estate corporations while being
powered by "Realty Generator".

This means they probably use that vast "locally connected" network to
generate geographically relevant leads.

Another piece of this puzzle might come from the Google logo on their
front page at http://www.realtygenerator.com/corp.html -- they even
say it's a "Partner", which is probably an overly optimistic way to
put things. Considering the type of service they offer, it's probable
Realty Generator uses Google's AdWords publicity medium to find the
number of targeted visitors a seller has paid them to find... while
still turning a handsome profit.

I hope my personal views (first-hand observations) on this matter can
be found to be useful.