It probably depends on which market you live in. In CO, it would likely be anywhere from 300-550 depending on your patience and the condition of the boat. As a craigslist boatwhore myself, I'd probably buy it at 350-400 if it was in reasonably good shape and I needed a creeker but you could maybe get more than that with patience since not everyone has a solid sense of what things are worth like I do
. Well known and currently active models (Mamba, Nomad, Jefe, Burn, Any Jackson) tend to resell better than older, discontinued or lesser known models & Riot Magnum is starting to fall towards the latter category.
I don't recommend selling to non-locals with a boat that size unless you know what you're getting into.