Apple

I'm a PC guy, kid is a Mac user. Grandparents had bought one for them and then 3 years later she watered it (on accident, at college). So I'm looking at Craigslist and other places to replace it but do I need to check if it's stolen? I can look at the "my computer" equivalent to make sure the specs match. But is there anything else I should look at to make sure it's good?

Thanks in advance