Most sellers are genuine. For the few who aren't, here are the little tells that say walk away.
If the picture looks like it came from a shop website, ask for a real one with today's date written on a bit of paper. A genuine seller won't mind. A dodgy one suddenly goes quiet.
A flagship phone at a quarter of its worth isn't a bargain, it's bait. If the deal feels too good to be true, it almost always is. Slow down.
Pushing you to pay before you meet, or refusing to chat properly, is the biggest red flag there is. On Handpass the whole deal happens in one thread — keep it there until you've met.
A phone-verified seller with reviews from real, completed deals is worth far more than a brand-new account in a hurry. Reputation you can see is the whole point of doing it locally.