Well, it could be simple & inexpensive or completely the opposite, the fact is you are not going to know until the car is yours & you can get a reader on it & reveal/reset the codes.
My guess is that the seller would have tried to have it reset already & it's come back on.
Personally, unless it's the exact car you want in the spec you are after AND it's priced to sell then I'd walk away & look at the plenty of other Zed's out there.