Personally, I would advise them on what's there and what the current code calls for. Things like lack of bathroom, kitchen, and exterior GFCI receptacles, lighting in utility areas like a furnace or boiler, and the condition the panel is in along with the grounding and bonding if it is lacking any from the current NEC.
I'll bet they just want to know that there's no bootleg crap work that was done and if it was can you please come clean it up.
And remember, a new 200 amp service will go a long way in being able to sell the house more quickly and today that means everything.
Good luck.