I've had issues with this mainly from my ex's side. I had him meet all my close guy friends and they became friends, so there was never an issue. He wouldn't let me meet his friends, and it turns out there was quite a few reasons behind that. I feel the only way there really can't be jealousy, and cheating, is if you both know your partners opposite sex friends that they are close with.

Me and my fiancé don't live around my friends anymore, but whenever we visit we hangout with them all the time. They are quickly becoming his good friends, and there is definitely no distrust or deceit going on. When we first started dating we both said goodbye to certain friends that we flirted with, or felt something could happen. We didn't tell the other about that, but ended up finding later. It was nice to know that we both felt the relationship had good enough potential that we didn't want anyone to ruin it.

You really just need to watch out for yourself, and look at your friends. If you think there's an attraction there, and you have a boyfriend/girlfriend, then you should either end the friendship, or the relationship. Having someone on the side is NEVER good.

But I really believe that you can be friends with the opposite sex, since most of my best friends are guys, and I'm a girl.

Of course you can be friends with the opposite sex. I have more close guy friends than i do girls and we are all so close but theres never any chance that anything would happen. It is totally possible and it's only a problem when jealousy takes over.