I'm maried so can't join in the fun, but for me I could not have sex with no emotional connection. I have to REALLY like a guy to have sex with him and the biggest turn on for me is the connection that starts in my head.
Years ago, pre- DH - I had a once a week relationship with a newly divorced man who told me from day 1 that he was not looking for another relationship- and that we were poles apart in what we wanted- he already had a child and an ex, I was mid 20s and looking for " the one".
I decided to keep on seeing him as I liked him. This lasted for a year. In the end he dumped me for another woman, then that fizzled out ad he came back to me, but by then I had met DH so we never met again.
I think the only way it worked for me was that although I liked him, there were some things that did put me off in terms of a long term relationship with him, so I wasn't too hurt when it ended. And as he had been honest from Day 1, I was able to keep a bit back.
In your case though, you need to be honest. There is lots of evidence around that fuck buddies do not work for women- someone was posting here last week saying that even germaine greer is now saying that the only people who really get much out of FB scenario is men.