Twenty four is not to old to start, though becoming a professional takes a lot of time, dedication, commitment and going without some of the things you like doing. I would suggest to have a fight first in America and if you still believe that becoming a pro is your goal then you should come our to Thailand, train live and breathe Muay Thai. Your skills will vastly improve very quickly, you will understand Muay Thai and you will become stronger physically and mentally.
There are opportunities to fight at all levels and you will get the experience needed to be better than your peers at home. It is possible to get an invitation letter from a Thai gym and get a one year visa. You can get by on an 400 US per month for training, accom, food, etc. Maybe the first time you come you want to stay 3 months then fight again at home then come back, up to you.
If you decide to come out here contact me, i will oraganise a letter for a visa and take care all all details for you in Thailand. I train at a small but famous (in Thailand) gym where you will get instruction at the highest level. The web site needs up dating but have a look at
www.muaythaicamps.com .
Good luck with your training, hope to see you out here sometime.
Tim