Do Therapists Ever Charge on a Sliding Scale?

I have recently been diagnosed with ADHD and am currently taking medication to help with the symptoms.  While this is helping, I recognize that I need regular therapy to help me better understand my condition and improve my overall self-esteem. I know that until I do this, I will struggle to improve my marriage and that when I land that next job, i will come across the same problems I experienced in the past.  I am recently unemployed however, and while I am on COBRA, there are very few therapists on my plan, and most have little if no focused training on ADHD. 

I have two questions that I need help answering.  1. Is it better to see a therapist with minimal background in ADHD vs. not one at all 2. Do therapist ever charge on a sliding scale based on your financial situation?  If so, how do I find out who they are?  I live in the Washington, DC area and I have had a hard time locating experienced (and not overly-expensive) ADHD therapists. I have inquired at the local universities with minimal success and am not sure what my next steps should be.  I appreciate any personal experiences or advice.