Well you got a lot of aspects to look at:
1. One major hurdler is do you have the heart for it? Martial Arts are an all or nothing thing that you have to devote yourself to wholly, without any second thoughts, if you want to become the best at what your doing. You have to be very disciplined and your diet is a major factor. Plus it's not easy. You will get injuries in training and there will be times when you hurt and do not want to go on, but you have to push yourself.
2. You also have to think what your going to do with these martial arts. Do you want to compete in tournaments and competitions? Or is it just for you learning and then passing it on and teaching someone else after many years of study?
3. Do you plan on entering Mixed Martial Arts/MMA? Where u need to know and be versed in many different styles. Some of the most practical fighting styles being Brazilian Jiu Jitsu, Muy Thai, Greco Roman Wrestling, and Boxing. These are top tier fighting styles that have been shown to transfer over to real fights better than many other mainstream fighting styles. However, it largely depends on who is teaching you. Many true Martial Arts masters will train you for years and you may still only have achieved a low belt, but this quality teaching would let you beat any black belt person who earned it at a neightborhood karate school where they hand them out like candy. It is much harder to compete in MMA, because most competitors are skilled in many different disciplines and you are fighting in the most realistic format possible.
A little note :Ultimate Fighting Championship (UFC) is the biggest professional Mixed Martial Arts organization out there. Hopefully you know of it :)
4. If you cannot financially afford this you will have a problem. You would need a job, but many people have managed to work and train just fine. It's all about balance in your life.
Hope this helped you out. Remember before training under anyone do your research, get to know their credentials to make sure they are giving you quality training. if you want to talk more email me at cpena9361@yahoo.com