How do MMA gyms work?

I'm a college freshman, and i want to join an MMA gym because i don't want to be the brawler type fighter. I'm not too big, about 5'10, 190. mostly muscle because i played Strong safety and outside linebacker in high school, so i'm not scared of some contact. I want to join an MMA gym, but i have no idea what the process is, or what to expect on the first month. how much does an mma gym charge? are they just gonna throw me in with the vets and say, goodluck? am i better off at a boxing gym? i feel like mma is better self defense than boxing. covers things like kicking, take downs, grappling, etc.
EDIT are classes mandatory?i mean i'm paying. what if i don't go because of school, or work? does my trainer get just as upset at me missing a class as my coach did if i missed football practice? how do i know what style they're teaching me?