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You need a bit of technical know-how to do this. You could post a question like this on freelance.com or something similar. Fetching data and making a site around that data isn't hard. But adding 100k unique content items is hard, manual labor. Best thing you can probably do is make pages around neighbourhoods or cities. The listings constantly change, but the cities and towns will always stay there. So tell something about that and link to the listings from those pages.