Solar city doesn't have a battery storage solution that I know of. You'd have to contact them to find out.

As for an inspection, I would think you could have solar city come out and give you a report on the system. Maybe not? Call their 800 number and find out. Maybe the current owner can have them come out?

Regular inspection should give you the best information - does the system look ok, is it still attached properly to the house, any signs of water leaking or damage. The inverter on the house should show a xxx wattage output during the day, see what it's output is. Good sunny day it should be producing 1500-6000 watts depending on size/panels.