By the way, the seller is not required to pay return shipping. This is Standard Practice and follows Paypal's Buyer Protection Policy.
When the seller is at fault (shipped wrong item, poor packing leading to damage, etc.) he may offer to pay return shipping. This is a Best Practice but again is not required.
Is it safe? Well, if you don't return the item with Confirmation of Delivery, you will not get a refund. If you do, you may get a refund from the seller or from Paypal.
That the seller is willing, if incapable, of sending you a label is a good sign.
Read his feedback and form your opinion from there.