Secondhand Marketplace Fraud: A Practical Guide to Buying and Selling Safely

Facebook Marketplace, Craigslist, OfferUp, and Poshmark have made it easier than ever to buy and sell used items. But they've also created fertile ground for scammers. From fake listings to payment fraud, here's how to protect yourself on every major platform.

Common Scam Types

Scam	How It Works	Target
Advance payment fraud	Seller demands payment before shipping, then disappears	Buyers
Counterfeit goods	Fake branded items sold as authentic	Luxury/electronics buyers
Overpayment scam	Buyer "accidentally" overpays, asks for refund of difference	Sellers
Fake escrow	Directs you to a phony escrow website	Both
Shipping fraud	Claims item was shipped but provides fake tracking	Buyers
Bait and switch	Lists one item, delivers a different (inferior) one	Buyers
QR code scam	Sends a QR code that links to a phishing site	Both

Emerging 2026 Tactics

• AI-generated product photos: Listings with items that don't physically exist
• Deepfake video "proof": Manipulated videos showing products working
• Cloned profiles: Scammers copy legitimate sellers' profiles and reviews
• Zelle/Venmo "business account" trick: Claims you need to upgrade your payment account

Red Flags Checklist

Buyer Red Flags (You're Buying)

• Price is significantly below market value
• Seller refuses to meet in person
• Seller wants you to pay outside the platform
• New account with no history or reviews
• Seller pressures you to decide immediately
• Stock photos instead of real product photos (reverse image search)
• Asks you to communicate via text/WhatsApp instead of platform chat

Seller Red Flags (You're Selling)

• Buyer offers to pay more than asking price
• Wants to send a cashier's check or money order
• Asks you to ship before payment clears
• Sends a fake payment confirmation email/screenshot
• Wants to use their "own shipping company"

Platform-Specific Safety Tips

Facebook Marketplace

• Check the buyer/seller's profile age and friends list
• Use Facebook Pay for purchase protection
• Meet at a Facebook-designated safe meetup spot if available
• Never share your phone number in the listing

Craigslist

• Cash only, in person is the safest Craigslist transaction
• Never accept wire transfers or gift cards
• Use a burner email — don't share your real one
• Meet at a police station parking lot

OfferUp / Mercari

• Use in-app payment for shipping protection
• Check seller ratings and transaction history
• TruYou verification on OfferUp adds a layer of trust

Poshmark / eBay

• Payments go through the platform — never pay outside
• Use the authenticity guarantee for luxury items
• Document everything with photos before shipping

Safe In-Person Transaction Guide

Meeting Location

Safe	Risky
Police station lobby	Seller's home
Bank parking lot	Isolated area
Busy shopping center	Late at night
Community safe trade spots	Inside their car

In-Person Checklist

1. Bring someone with you — never go alone for high-value items
2. Inspect the item thoroughly before handing over money
3. Test electronics on the spot (charge, power on, check screen)
4. Verify serial numbers against the listing
5. Pay with cash or instant transfer — no checks
6. Share your location with a trusted contact

What to Do If You Get Scammed

1. Screenshot everything: chats, payment receipts, listings, profile
2. Report on the platform: every marketplace has a fraud reporting system
3. File a police report: especially for amounts over $100
4. Report to the FTC: ReportFraud.ftc.gov
5. Contact your bank: request a chargeback if paid by card
6. Post on scam databases: help others avoid the same person

Sharing Personal Info Safely During Transactions

When buying or selling, you often need to share your address, phone number, or payment details. Sending these through iMessage or Messenger leaves them permanently in chat history.

With LOCK.PUB, you can create password-protected, self-destructing memos for sharing sensitive transaction details. Your address or account number disappears after the other person views it.

Safety Summary

Principle	Action
Verify first	Check profiles, reviews, and pricing
Stay on platform	Chat and pay within the app
Meet safely	Public places, bring a friend
Document everything	Screenshots of all communications
Trust your gut	If it seems too good, walk away

Secondhand marketplaces are great for finding deals, but the best deal is one that doesn't cost you everything. Stay vigilant, and when you need to share personal information during a transaction, use LOCK.PUB to keep it encrypted and temporary.