let my enemy ride in my truck?

[Fred]

i have a friend/roommate which he and i will buy a truck together and sharing it...match the payments and gas but i have a enemy who is friend with my roommate, is it ok if my enemy rides in my truck that i am paying for, but also he paying for it too....wondered about your opinions because i dont feel right, i am feeling bothered by this...but havent talked to my roommate yet