It used to be called a "gift" but last time I used it, it was "send money to friends or family". It's secure in the sense that you're not giving bank details away and the money should get to the right account if you give them the right email address, but unlike with a purchase there is zero payment protection. It's basically like posting an envelope of cash to someone. As you're the seller and if you make sure you have the money in your account before giving them the bike there should be little risk to you. They can't do the common chargeback scam and say they didn't receive the goods because as far as Paypal is concerned, there were no goods, the nice person just gave you some money.