I haven't done any research on this, but I would have to think that being a doula would be your best bet financially as you should be able to set your own prices as well as hours for scheduled appointments, though obviously not the actual births. I'm also, maybe falsely, under the impression that the schooling (if there is any, I honestly don't know much about it) would be shorter than say, if you were going to be an EMT for the county. I do know a bit about that as a very close friend of mine went through that gruelling school a couple of years ago. She did get paid while she was going through it, similar to if you were in a police academy, but the pay was low, and continued to be low once she was on the road for the first 6 months until she completed all of her training. She is a very smart woman & said that it was the hardest thing she's ever been through (and she's been through Delaware State Police Academy, known to be the most difficult in the nation, as well as being a volunteer firefighter, so she knows from physically, mentally & emotionally taxing situations).
Here's what you need to do: sit down & do a pros & cons list & see which would honestly be the most fulfilling for you & go from there.