What happens if a person drives without correct license?

hello, a friend of mine owns a limousine & its registered under personal use, what happens if he offers limo service and doesn't have the correct license to drive it? sorry maybe im not being clear, i guess you need a special license or something to drive a car which has the same purpose as a taxi rite except that this is a limo. if he gets pulled over for some odd reason and they see that hes driving people around what would happen?