Don't be ridiculous. If the guy can ask you to have sex, he can ask any others down the road. This guy have no respect towards his gf, himself and to you. Further to that, why need to feel the pressure to give in. Sex is not charity and remember, whatever you do, it comes with consequences. There are a lots of cheapos out there looking for free stuff, but remember these people sleeping here and there may have contracted diseases which you may not know of and medication is not cheap. Be wise and think about it.
Dont spend few minutes of enjoyment but regret for a lifetime. And yes, I agreed with others, stop communicating with your cheapo friend. He is not worth your attention. He's only interested on getting someone on the bed.