When building a startup for long-term success, the team should avoid mercenaries.
One simple reason for this is that mercenaries think for the short term and about themselves first. They want the best outcome for themselves and, when the ship is sinking, they will be the first to disappear.
If paid more, mercenaries will also fight against you in the battle by joining hands with your competitors and sharing internal secrets.
So make up your mind, decide and hire accordingly on the traits. Think for the long term and overall win-win for the organisation.