I don't see this thread ending well. That last comment sealed the deal.

This 'relationship' is NOT going to end well either. T
ake it from someone who has been there.

And oddly enough, I had a long sit-down last night wiht one of my closest male friends who was having a guilt attack because he was starting to think that HE was doing the same thing, and I told him the honorable thing is simply to end it and cease all communication with the 18 year old girl- not woman, GIRL- in question, who I have a great amount of respect for personally. She's old beyond her years but that doesn't mean she doesn't have the emotional issues of a teenager still.
Look at yourself honestly. Look at HIM honestly- trust me, older guys who are worth dating are looking for a mature woman who is a potential partner. Not to be cruel, but he almost certainly looks at what he's got going on with you not as a relationship at all, but as a fling.

Do what you want. I could tell you, "Be careful and protect yourself". But the only way to do either of those things is NOT to put yourself in situations where there is an imbalance of power. And this one is WAY outta whack.

Oh- and providing a minor with a 'bottle of lemon bacardi'- and then having sex with her- that's simply disgusting. Shame on him.