What is this? Someone with common sense here? Madness!
I don't know if it's "healthy", but it is natural... most humans share similar thought processes...but each person chooses what they allow themselves to continue thinking upon... when it comes to sex, its no different. there is a bell curve...we don't know where the majority lay, but at least one more person in the world will think whatever you have thought.
why thank you sir
Of course, it would depend on the situation. If acting on them will get you into legal trouble, keep it to the mind.
depends on the fantasies