properties is a more general keyword (properties) for the specific keyword (. It will not hurt any to have this keyword there b/c it should be on topic of the specific keyword. In the mega tags section I would do it in opposite order and with added combonations like this (starting most specific to more general) .. san diego single family, san diego two family, san deigo apartments, san diego condos, san diego vacations homes, san diego, ca, single family, two family, apartments, condos, vacation homes, properties, realtor .. this will give you more possible search results listings b/c it has more keywords .. .. with the above methods 1,2,3 .. you really only have 3 words in the title for possible results listings. EDIT: .. I think i understand what your saying now .. I only added that if they wanted Properties as a subsection of their main page. If the entire site was Propertie listings .. then it would look like this .. Realtor.com > CA > San Diego: single family, two family, apartments, condos, vacation homes .. .. but i think putting 'Properties >' or 'Real Estate >' as a subcatergory would help A LOT. Other wise your missing the main keywords that will land you key listings.
SEO-wise all titles are the same. But for a live visitor they're not... personally I'd prefer option two, but that's just my taste.