Agree with others, the Craigslist/Facebook market seems to be pretty solid for that sort of stuff right now. Just make sure you take some good pictures, maybe shoot a short video walkthrough/walkaround that you could upload to youtube and post the link in the sale listing. If you do that, sign up for a new Gmail account first, and use that as your youtube profile so it's not connected to your personal info too closely.
Only sell to someone in person (no out of state, I'll come pick it up, I'll pay to ship it, etc. deals), cash in hand or a cashiers check from a locally represented bank that you can go "hammer" in person and cash before handing over anything. As an example, don't take a cashiers check from "Southern Mutual Bank" or some BS that no one's ever heard of. But taking a cashiers check from Wells Fargo, Chase, BECU, etc. is totally fine, just make sure you verify and "cash" it before handing over the title and trailer. Most people would probably just meet you at the bank to handle it, which is easy enough.
Frankly, you'll probably find a like minded person just looking for a camper to get out with their family for the summer, and it'll probably be an easy and fun deal.