Being friends with opposite sex is possible if the two are honest about their feelings. I have a lot of guys friends than girls and I have no sexual attraction for them. I see them as my brothers and I discuss my romantic life with them.
The problem is overtime feelings can grow when you share a lot of intimate things with a person. But if you see your friend of the opposite sex as you see youbthe sex friends, you can overcome the temptation of getting intimate with them.
Although, I have had some of my guy friends fall for me. Sometimes it ends up in just sex and that's all.
My advice is if you can’t control yourself with the opposite sex, then don't keep them as close pals.