i got an offer in the mail that said i'd get paid 25$ per referral to nextdoor.

None of the leads that I know are financially rewarded, they are just the people that happen to start the neighborhood and are often the most involved in making it take off.

I think what the above poster is referring to is the referral program where if you invite someone to Nextdoor AND that person starts a neighborhood, you get a $25 Amazon giftcard. I've personally invited a few people to Nextdoor, but all of them already had a Nextdoor website for their neighborhoods so I didn't get anything even though I referred them.