Only the host gets the profits from playing with another user, no matter the platform.
VG247 has a rather worrying report about the upcoming features of Far Cry 5. Just as a reminder: the game is offering a possibility to play the whole campaign in co-op, from the very start. Unfortunately, as it appears, the progress will save for one player only.
If the rumors are true, we should expect that only the host will have his progress saved and the second player will serve as a companion, having to finish missions for the second time (or in co-op, once again, but as a host).
As for now, it’s worth waiting for the official explanation from Ubisoft. A lot may change until February 27th, when the game releases on PC, PlayStation 4 and Xbox One.