Does not make sense for me as random event. Who pays the big amount of money to hire them, for what? If it had political reasons, then it should be late in the campaign and the player had a certain high position, otherwise, why? Such a high ranked person should have bodyguards and wear some form of armor perhaps when going through some shabby streets.
If it were a certain event/quest with a story and an assasination could be expected, the player should be able to prepare for a situation, like wearing some armor in towns.
On the other hand, there could be kind of robbery attempts in towns in certain areas. But not that often, please.