i train at grindhouse and been doing it for about 9 months now. i'd like to eventually compete twice a year and ultimately become pro. i still have a lot of learning to do but getting kicked in the face and choking out dudes bigger than me for a living is better than framing and hanging drywall.
it's fun; always something new and never boring, you'll be in great shape, and it can potentially be a full time job if you do it right. but there's a lot of self-preparation involved, and it's not as simple as just working out, hitting the heavy bag, sparring and grappling all the time. it takes a shitload of commitment that frankly, 99% of people who walk into grindhouse for the first time and say they wanna train in MMA don't have. most people quit after a week, and the rest after a month or even two. trust me, you'll never get used to getting your face pounded, you'll lose your flinch in time, but it still hurts getting knocked around. if you're serious about it, the trainers will push you til you break, break you some more, and expect you to give 200% every single day, 7 days a week and not waste their time.
and if you eat shitty food, have a serious relationship or multiple pets, consider changing that. if you decide you're fighting full time, unless you're a heavy weight you need to eat good nutritious food and eat often (5 to 6 meals a day...skip the pizza and beer), your girlfriend isn't gonna get cuddle time or sex because you're not gonna be around and will be too tired to perform (not to mention it's not easy for someone that cares that much about you to watch you get knocked out for a living), and you'll never be home to feed the puppies or scoop the cats litter box.
i do encourage everyone who's considering to at least try it out. you never know it could turn out to be something you're really good at. especially the stocky guys with high school/collegiate wrestling backgrounds, they're always tough as nails. also be prepared to sweat, i drink a gallon of water with electrolytes every training session and sometimes i'm still dehydrated by the time i'm done. i'm not trying to discourage anyone, just saying that if you think it's something you may want to do, come ready to work.