FWB: basic ground rules needed

[DeusExMachina]

Recently, a friend of mine expressed to me that she wants our relationship to become physical; moreover, a friends with benefits relationship. I would like to know some basic ground rules we should establish to help ensure the survival of the friendship(not that it's even possible) when things change in our lives that the FWB ends. I truly value the friendship we have built up over the past few months and am a bit apprehensive since this may totally destroy the friendship.

 

Back story if it helps with what rules I should apply:

We meet about 14+ years ago in college and were in an FWB relationship. After a few weeks I started to develop feelings for her and started to get scared. At the time I was 19 and she was 18 with a 1 year old daughter, I was not sure i could handle the kid at 19 and bailed on her. She obviously had feelings for me and was very hurt by it, which I always have felt bad over. We went our separate ways and never saw each other again for the past 14 years. During that time I got married and had 2 beautiful girls and just recently got divorced. My ex and I grew apart over the past 2 years and the divorce was a mutual decision. I rejoined the dating world dated for a bit and randomly came across her on Facebook. We eventually went on a date. I had not expectations for the date other then to catch up and apologize for being an coward 14 years earlier. It turned out to be the single most amazing date I had ever been on. She told me that it was amazing for her as well. I've learned that she was in an 11 year semi-long distance relationship that she put an end to permanently in December of last year after being devastated by finding out her ex had a completely separate relationship in the other city he worked out of. We made out in the beginning, but when I expressed my feelings toward her she told me she saw me as "just a friend." I no longer pushed that and just enjoyed my time hanging out with her as a friend. I would only communicate with her if she initiated the conversation. She continued to want to go on "dates" and told me how much fun she had with me and how wonderful I am. Just before Christmas she seemed to really "open up" to me emotionally and I felt I should test the waters again. After another amazing "date" I went for the kiss and was turned down nicely. I was very embarrassed, but she didn't seem to phased by it and even invited me over with her and her family on Christmas Eve. When she asked to come over to watch a movie at my place and she expressed that she want us to be FWB, I was floored to say the least. I learned that she wanted to kiss me when she turned me down. but was afraid I would think we would be in a relationship then. She said she doesn't want a relationship now since her last relationship was very oppressive and she is re-discovering herself. She said she is worried that she will hurt me. She also said the following day about the same subject that she is very scared... I kind of get the feeling that she really is the one scared of being hurt. I've been in a few FWB in the past and they always end up with her becoming very emotionally invested and a little messy afterwards. I'm kind of hoping she does and it leads to more then a FWB relationship. I'm not one to obsess or get attached easily, but I have stronger feelings for her then just a friendship; however, I'm not afraid of being hurt. I know that is the wrong reason to start a FWB relationship, but I also have my physical needs and I really am one who enjoys lots of sex. My intentions are dual purposed.

 

Any constructive comments or suggestions are greatly welcomed, thx!