If your states allows, you can just practice psych with FNPs (if you are comfortable about scope of practice issues)- usually the states that allow this is not independent practice state and they are ok with this since there is supervising psychiatrist anyway. Regardless, you just have to consult BON for this. Extra training is not as important as finding someone to hire you. In some states (OR,AZ,WA,IA, MD, and Texas too I think), the mental health practice is restricted to only psych NP. I still think post-master is the best option in case you have to travel to other states that require this. Even though it is not require, some employers prefer the board certification anyway.