Cam chain rattle would be one thing, when you start the bike up if it needs doing it will make a noise similar to a sewing machine.
With some bikes it will disappear when warmed up,and with others the noise will stay,
It's a bit of a tricky one because my chain was replaced around the 30k mark, it's now on around 45k, and last year it rattled for about 7 months then the tensioner finally clicked another notch one day and it all went weirdly silent, i actually thought something was wrong 'cos i was standing next to it without a crash helmet on when it happened.
Although i only do short journeys to work, mainly through heavy traffic, so i'd imagine that was the main reason why it took so long to find the next notch on the tensioner.
Other than listening, i would just ask the question if it's been done recently or not.
This bike does sound a bit ropey anyway to me, but you can clearly hear the rattle.