I've only ever ordered one thing- a new motherboard for my washing machine. Sellers on Mercado Libre have ratings from customers- this guy had been selling on Mercado Libre for years and had a top rating. But I got a Mexican friend to call him for me (I'm pretty fluent with spoken face-to-face Spanish, but they talk so darn fast on the phone) and he seemed totally legit- had an appliance store in Mazatlan. He gave me his bank account number, which I paid at Oxo (no need to use Paypal), scanned him the receipt as requested, and it was delivered by Estafeta 2 days later. But I'm not sure if I'd order an iphone that way. Could even be stolen. I doubt there's big black market in stolen washing machine motherboards 🙂