Seeing as the Verizon iPhone 5s are sim unlocked, all you have to do is remove your sim card and whoever buys it can use it on any GSM network. If you do not remove it from your account before selling and the person who buys it, wants to use it for Verizon (CDMA) it wont work. It must be removed from your account before it can be activated on another Verizon account. This applies to Verizon only.
I would suggest you replace the line with another phone first and then sell the phone. All you need to do is remove your sim and just list on eBay.