I have bunch of expensive used clothing to sell and I know a guy who is a high ranked seller on ebay and Amazon. I asked him over the phone whether he can sell them for me for a fee if I ship them to him. He said he can. I really trust this guy but technically if he ever decides to run away with them there is nothing I can do. I think I need to get some sort of a written guarantee of payment but I am really hesitant to do so because it would look like I am suspecting him. What should I do? Is there a polite way to ask for this?
A contract, as has already been mentioned, but be sure to address all terms. Are you selling him the clothes or is it a consignment situation? You then need to determine either the price, if a sale, or the split of proceeds if it is a consignment. What price are you authorizing him to sell them, $5 per, $25, $100? Can you request their return if he hasn't sold them, and at what point? Who pays to ship the items each way? Risk of loss, during shipment there, during consignment, during possible return shipping?
It is essential to determine every possible outcome that you can imagine.
It's called a contract and don't be ashamed for asking for one especially a stranger online. There's nothing wrong with writing down expectations for both sides and agreeing to it in writing. Even if it's a friend this is a good way to lay it all out in black and white. Anyone who doesn't agree to it isn't serious about holding up their end of the bargain
Giving him a contact is not impolite, it's just how business is done, and it doesn't just protect you, it protects him too so the terms are agreed on in advance.
Still better than nothing because it gives clarity and you can have something to refer back to if you forget what you agreed. Doesn't stop someone being malicious of course