I would agree that having a boat that is well-maintained is a good thing. Unfortunately, this isn't always what happens through a charter company. Our new power catamaran was not that well maintained - the fuel filters were never changed, it appears that the oil in the generator (well-used by the charterers) was never changed, let alone the fuel filters. Other minor irritations. Good thing we bought it so soon in its charter life.
We met a fellow at the Panama Canal many years ago who had gone to St. Vincent in the Caribbean to check on his new boat, left there to be chartered and earn him some money before he retired completely. The boat was a diaster, and he thus chose to cancel his contract and bring the boat back to his home in california. The trip from St. vincent to the Canal was just one failure after another. Engine problems, broken sail hardware, blown out sail, on, and on, and on.
A good surveyor, and a careful check of such things as fuel and oil filters (how dirty is the oil?. are the filters rusted into their housing? .....)
Hate to be a wet blanket, but better to know ahead of time what you're facing.