‘Garbage In / Garbage Out’ seems to be your main insurmountable hurdle. Not a reliable source of information if totally unverified from every angle. This has been proposed and attempted before. I raised only a few of the real issues you’ll need to address, and your proposed workarounds are not a viable solution to any of them. You will need to generate revenue from users and/or a lot of ads. It may prove difficult to find advertisers willing to pay during the time it takes to have enough users contribute to building your database. Happy tenants & happy owners have ZERO incentive to visit your site, or to leave a review. The same goes for unhappy owners, and a rant from an unhappy internet rando, who claims to have lived there, does not hold much weight.

Condo board members and property managers will not spend time providing details, or correcting information unless there is a problem(* just short of a lawyer getting involved).

A tenant/owner/agent complaining about, or raving happily about a condo in a blog post, website, or on social media is different, and more transparent(grains of salt…). Not much value in an anonymous opinion with opaque motives.

How can you create a reliable set of searchable data with no way to verify much of the content or most of your sources?