With your background in nursing, I would join up with a SAR (Search and Rescue) group and train my dog up. This would be more of a hobby and allow you to keep your current job. Most SAR groups would love to have a nurse on board. While you are training and getting your dog certified, they would probably partner you up with an experienced SAR K9 handler for both training and call out searches (always nice having a good medic with you when you find lost people).

Becoming a professional dog trainer would be like being a little league coach: teaching basics over, over, and over again along with dealing with irate idiot fur children parents.

The other two pieces of advice I would give is:

1. The ideal dog is calm, controlled, and confident.....strangely enough, the ideal handler has the same traits.
2. The only time two dog trainers will agree on something, is that a third dog trainer is doing it wrong.