Do they recieve it on facebook?

[Samarth]

Remember to read this all, i typed all of this just for you-

a person whom you're not friends with will receive your message, if they have allowed it in their privacy settings. though, facebook is recently been rumored to roll out a new practice in which you will be charged if you send a message to someone out of your circle.
If they are your mutual friend (friend of someone you are already friend's with) you have high chances of having your message delivered.