Good advice so far. Charter boats get a lot of abuse, especially in these areas:
Sails, expect to replace them, they're likely beaten up by now, although sometimes you get lucky and it's already been destroyed by someone and replaced recently. Same for the rig. Standing rigging is due a replacement anyways. At least would do a thorough inspection by a rigger who knows what to look for, including chainplates. Furling gear likely to have been abused with winches - check drum and if it rotates easily on the forestay. Unreported groundings are commonplace, but a surveyor should find if there are any problems in that area. Bad parking and dragging anchor are everyday events in charter use, so make sure the topsides are checked for delamination. Windlass sees a lot of abuse too, and with it the bow fitting. And the engine will have many hours on it and occasionally been repaired (bodged together) in a hurry so people can continue their journey. Water tanks are sometimes filled with the wrong fluid (water in diesel or diesel in water) and not always perfectly cleaned up afterwards. Interior will look a bit banged up and the toilet is usually half broken. Those are the things to look out for - not all ex-charter boats will have all of them of course.
Pricing should reflect the state of the boat.
On the upside, you can expect to find a basic dinghy and working outboard in the inventory. Otherwise charter boats tend to be equipped with the bare minimum, so expect further spending to fit whatever equipment you desire.