I've never sold a vehicle before - and indeed never bought one 2nd hand from a private seller (only ex-fleet from a dealer) so it's all new to me!
I'm already struggling to price it because it's not exactly a camper but it's definitely not just a box van (windows / insulated & lined / seat that converts to bed / lights etc etc but no kitchen).
But then added to that I have no idea how much people would expect to negotiate down on a private sale.
FWIW it's quite old (15yrs) so cheap-ish but in good nick as you'd expect of something basically used for travel to events & sleeping, I don't know if that makes a difference.