1. MMA gyms are WAY more expensive than many other martial arts gyms or dojos. Even the best deals are $100+/month for membership fees. Compare this with boxing gyms where the prices are around $40/month. If you're poor, MMA can be especially tough to break into.
2. There are a fair amount of women who workout at MMA gyms. They seem particularly interested in boxing and kickboxing but there was also one in my BJJ class. This may be an incentive for some of you.
3. You should be in good shape before you start. These gyms often advertise saying that you don't need to be in good physical condition beforehand, but I disagree. You can't expect someone who is severely overweight or very weak to do takedowns and be repeatedly taken down for an hour.
4. Wrestling is by far the best base for MMA. If you don't know how to wrestle and want to do MMA, then start wrestling. Even if you are more of a striker, you can benefit from learning takedown defenses and escapes from the ground. The only reason I was able to keep up with guys who had been doing MMA and BJJ for several months to over a year (even though today was my first day doing any of this) was because of my wrestling background (which isn't even that extensive). In fact, the only guy who I really had trouble rolling with was a dude who wrestled in college. He easily took care of all the wrestling moves I sneaked in. The others had trouble taking me down, didn't really know much about wrist control, and couldn't really submit me. (Then again, it could have been the people I rolled with more than BJJ itself.) There's a reason why many of the best mixed martial artists are also wrestlers (e.g. Randy Couture, Chuck Liddell, Tito Ortiz, Jon Jones, Dan Henderson, Dominick Cruz, and many others).
5. Despite my praise of wrestling, I will say that wrestling is not complete. My stance was initially too low which made me vulnerable to knees and kicks. Submissions are still foreign to me and so are guards (since a wrestling match is over when you're pinned). BJJ is a nice complement to wrestling. Alternatively, you can just ground and pound the guy once you have strong ground control. That said, you should also learn a martial art like boxing or Muay Thai to develop your striking skills.
6. MMA is a great way to get in better shape! I hate running so I'd rather grapple or strike something to condition my body.
I'm going to try kickboxing, wrestling, boxing, and maybe even some kung fu in addition to more MMA stuff. Anyways, you should give it a shot!
(Note: For MMA classes, they might ask you to take wrestling, BJJ, and kickboxing classes beforehand. However, if you're a wrestler then they'll probably let you start right away.)
