Hi, welcome janna;
I'm a nursing student and currently certifying to be a doula. Here's two threads (not long) that convinced me to be a doula:
http://allnurses.com/forums/f35/glor...es-139427.html
http://allnurses.com/forums/f35/doula-150988.html
Those threads will answer some of your questions.
I would definitely recommend it if you're interested in birth but you need some flexibility in your schedule.
There are several certifying organizations, DONA being the biggest and most well known. There is also CAPPA, ALACE, and ICEA. Who is better is a matter of opinion. I'm going through DONA because the training was sooner and it has a bigger base and reputation.
You have to read 5 birth books from their list, become a member, attend a 3 day workshop, log a certain number of hours doing it, and some other writing. The length depends on the org and you.
The workshop is about $300 plus the books unless you use the library. However, you'll need the books for reference. There will also be the cost of various supplies you'll want to bring as decided by you.
You're eligible.
You heard right about the price range. Doulas, as a majority, are freelance. There are doula service groups that you can work for where they'll send you referrals. Look for a doula group or service in your area and give them a call/email.
Hope this helps and if you have any more questions, just ask.