Trust works both ways, the buyer sends you the money, you send the laptop. If you are using paypal, make sure the money is in your paypal account and then immediately transfer it into your own bank account before you send the laptop because it is very easy for the buyer to raise a dispute which will cause paypal to put a hold on the money. If you've transferred the money out of paypal, there is nothing paypal can do. Just make sure in any selling description that funds must be in your paypal account before the laptop will be sent. Or use a delivery service that comes with insurance against lost or damaged items. That way if the buyer claims they never received it, you can claim on the insurance and let them deal with it.