It depends on the individual state you would like to teach in - each has different requirements. I came into SPED with a degree in counseling and I had to take 11 classes to become certified, another 5 if I want to pursue a Master's degree.
If you find you are interested I'd suggest sending your credentials to the state department of education for evaluation....they can tell you what requirements you will have to fill (as in classes), any state tests you have to take, the steps to get licensed once you have everything in order as well as suggestions as to what colleges / universities may offer what you need.
SPED is very stressful but also very rewarding. I always tell those interested in SPED to be prepared that only a portion of your work involves actual teaching & prep- you will probably spend double the time with case management, paperwork, and meetings!
Judy