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catads, weblinks and xdirectory modules COULD all provide the right solution. But you will need to change some language definitions and maybe templates to get it right.
What you will have difficulty with is the filtering process; for example, you wont be able to offer searches which filter 'City' and 'address', with 'price' by using selectors. I don't know any module that offers that level of search filtering, except as part of the search string of course.
I think weblink on happy-linux will give you the best options. It allows multiple catagories for every entry, which means users will be able to select internal categories to manually filter their views. Also gives automatic google map views taken from zip codes.
Its a very comprehensive module and worth a look. see here
http://linux2.ohwada.net/also take a look
IBDeeming real estate moduleedit: also I just found this
http://www.torrecanela.com/portal/modules/realty/
