I agree with the previous comment. Liquid damages create corrosion over time and the longer you leave it the more difficult (costly) it becomes to repair.
If you are comfortable with opening the case and removing the logic board and inspecting / cleaning that’s a good idea.
Otherwise I recommend to get a technician to have a quick look at it to ensure nothing ugly brewing.
Depending on which country you are in, there may be lost/stolen databases where you can check the serial number against. I’ve got the strict rule of not buying if the seller is reluctant to share the serial number before the sale is agreed.