Alright what do I do? I am confused?

Alright so I'm a bit freaked out guys. I'm 19 and I live next to this married couple in their thirties. They have an open arrangement and the wife (who's smokin hot) has taken a shine to me. I had drinks with them once and the dude told me he'd like me to hook up with his wife as he works out of town a lot and wants to keep her happy. Is this normal for married people? I mean I get that some relationships are open and some aren't. WTF do I do?