Depends what type of realestate site is it? Does it sell realestate or is it just a realestate information site? If it is an information site you should first go for .info - but if it sells property you should go for .org then .biz
I would go for .us if that is the market you are aiming at - .info if it is just for an information site and I would'nt bother with .org or .biz at all.
You could focus on Los Angeles (.LA), South Carolina (.SC), Maryland (.MD) or Deleware (.DE) states by using those extensions. Not "logical" choices but high brandability. I've done this with several of my names and think it will pay off in the long run.
another opinion needed - will a name have value with the word realty next to it with a place in usa eg- newyorkrealty like that
and does all place name in usa have value in realestate names business