OK, I almost fell for a fake airbnb site scam too. It looked so real and, being somewhat tech savvy, I couldn't understand how the transaction could be risky if it went through the airbnb site. So, I called my very tech savvy son who explained it to me. So, here we go.
In my case and in lots of examples on this site the fake links look like this: "https://airbnb.com84-rooms-checkin.net/blah/blah/blah".
You look at the "https://airbnb.com" bit and think, well that's airbnb alright, what can go wrong? But that bit is not actually the airbnb domain - its a subdomain (which can be any prefix before the actual domain). The actual domain name in the example above is "com84-rooms-checkin.net/" which is what tricks us all.
The thing to look for is the "/" which marks the end of the domain name (or nothing at all if there are no sub-folders in the domain). So, an airbnb URL should look like this: "www.airbnb.com/blah/blah" or just "www.airbnb.com". The stuff after the "airbnb" bit and before the "/" should never look like this: "com84-rooms-checkin.net".
Good luck!