Potential problems of private security. (I’ll also going to roleplay an asshole wealthy person.)

When i watch We Can Make A Better Guard by Desks And Dorks, and when he start talking about the second types of guards, which are funded by wealthy citizens, nobles, and church officials, he said they would act like gangs since they are funded by different people that have their own whats and needs, and that they don’t want to deal with their rivals. Probably even their employed guards have them too.

Would this happen in a modern ancap society?