if you havent visited this website, check it out because it asks a lot of the right questions http://www.doula.com/become-a-doula.shtml
it is an awesome thing to be with labouring women, and to be witness to their birthing experience..... really touches the realm of sacred, imho.... if it is what can get you out of bed at 2 in the morning with a sense of compassionate wonder, then heck yeah!! go for it!!!
back in my childbearing years i was a passionate advocate for **safe childbirth, and chose to have the births of my 4 kids ( and a 2nd trimester miscarriage) in what i felt was the safest environment for me and for them, and that was at home.... i had midwives and good friends who acted in the capacity of a doula, so i never had that as a separate service, but since the norm in the US is hospital birth or clinic birth, it seems to me that there must be a career path somewhere in there......
one of the coolest things i have ever done is labour coach a "sister" in the first vaginal birth of twins ever seen at our community hospital..... nurses who had been on staff for 20 yrs had never seen such a thing...... 3 doctors and only ONE had ever seen it.... somewhere on the african continent!!! one doc commented after over a 2 hour wait for the emergence of the 2nd twin " this first one will have teeth before the other one shows up"...... that is the mindset when the practice, the "standard", the norm is to haul the babies out of a surgical incision!!!!
good luck with your exploration and decision making on this matter!!
** i became self-educated on the subject and attended hearings of the medical boards when legislative actions threatened choice for women by squelching the practice of midwifery.... i sat on committees with midwives to help develop a "standard of care" for homebirths and midwives that was so enlightened in terms of developing a rationale that didnt treat childbirth as a medical emergency