FB Marketplace Scam. There's a second where they get your phone number and send you a "confirmation" link which apparently will confirm you are changing an account over to them. Not sure what account, as my phone provider auto blocks these scam links.
This one is pretty stupid. Instead of venmo'ing the cash to their "relative" who is coming to my place to pick up the item. They expect me to accept the Venmo on my end, then wait 1-3 business days before actually being able to get the cash for the product. At which point there is no cash. They continually try the scam even when I say it's cash only.
Also if you inspect these profiles they are generally one image and zero information. These are all from fake accounts which they delete /get banned periodically.
Pretty sure there's no way to cancel a venmo payment. Once it hits your account it's there. Idk what 3 day thing you mean.
The only fishy thing with venmo is the "I sent a code" or saying "I sent it" and sending you a fake confirmation. Like unless it's in your venmo account it's not there but I don't think there's anyway to undo it. Otherwise what good is their service? It's not like they can do a charge back. That's why theft on venmo and similar apps is a big deal because they can't/won't "undo" it.
This isn't like getting a direct ach payment/check to your bank or anything.