I was intrigued by the topic of this thread, but having read it, it doesn't seem to have anything to do with "Big Data".
If you combined ever assessor record, every recorder record, every MLS record, every appraiser record, and every property management record in the US for the last 30 years, you're not really in the realm of big data. You could use big data tools for that if you want to, but you certainly don't need to.
Maybe the OP could clarify the goal. Sounds like maybe he was suggesting something similar to what McDash did for lenders - aggregate anonymized loan level data from every participating lender on every loan they made including payment history (still not big data btw). The participating lenders benefited from being able to benchmark their loan performance against others and gain insights on what loans were or were not performing well.
Could be cool for investors as it would give insight into real rates of return, real expense ratios, what product types perform best, vacancy rates by area and product type, lates by area and type, etc.
If that is the goal, I think the primary challenge will be defining a common dataset across real estate investors, and then getting those investors to consistently report their data in that format. There are far fewer loan servicing platforms then property management platforms which simplied the job for McDash. Also took far fewer participating lenders to get to 70%+ of the loan population, so again far easier for McDash. And major lenders likely have much deeper pockets, again making it a far better market.
Given the lack of consistent platform, the large number of investors, their relatively smaller financial interest, and their lesser degree of technological sophistication, my guess is that this idea is not viable at this time as a separate company. If I ran a property management software firm and was getting the data for multiple customers anyway, I would absolutely consider adding a benchmarking feature. Plenty of precedence for this, even quickbooks has some weak features along these lines.
Note that McDash is now owned by LPS, who is now calling themselves "Black Knight Financial". Interesting name choice after their role in robosigning, etc.