doesn't matter what you used to do although life experience adds to your ability to practice so good trainings sometimes have a minimum age requirement.
to be fully accredited you need to train for a minimum of 4 1/2 years.
for good employment prospects at the moment train in CBT (cognitive behavioural therapy) although tbh by the time you finish that fad may be over with.
best to do a foundation that gives you a taste of several different models and then decide.
it is very expensive as not only do you have to pay for college fees but also for your own personal therapy (which will last the duration of the training as a minimum) and sometimes for supervision if your training doesn't provide it.
if you've never had long term psychotherapy before, prepare for a rocky road, and prepare those around you...it is tough and will lead you to question every aspect of your life.
there is a high drop out rate due to both the above factors.
have you asked yourself why you want to accomapany people through their misery and pain on a daily basis....it is probably because you are wounded in some way yourself and if you find that idea repugnant then i would say this road isn't for you.
on the plus side it is priviledged, fascinating work. not a way to ever get rich though!
if you are still interested after this post....it might be for you!
hope this helps and feel free to ask any further questions!