Borderline inappropriate?

Im 18 and I've been talking to this guy that is 26 but this guy refuses to tell me anything about his life and he has made it very clear that he wants nothing more than casual sex. Part of me feels bad because of his secrecy even after talking for a few months he can't seem to tell me anything. We haven't even had sex and it just gets out off. I don't think this is a friendship because he isn't telling me anything and treating me like a good friend. I know this is not a relationship. And I don't believe this is a friends with benefits situation because we haven't had sex. What is this? What do I do?