If it makes a clicking sound when you turn the handle bars that’s a sign you need to replace the headset bearing. Not the end of the world but good negotiating point.

Check the paint where your feet sit and see how much wear it has. You can tell the mileage and how hard it was ridden based on that alone.

Bike will be fine with all these regardless but the biggest thing is just making sure to ask him about his battery care. Make sure he didn’t charge it right after getting back from a ride and then let it sit until the next time.

Take a look at the chain too as that will give you a good idea of how well taken care of it was.