What are the reasons that Castle might or might not want to legitimize his investigating via becoming an actual licensed private investigator in the state of NY?  I was looking into the requirements for a PI in NY and the one thing that stuck out was the experience requirement;  http://www.dos.ny.gov/licensin…..faq.html#1

Based on the story line could he actually apply to take the test and get his PI license? Think about it, he has been 'partners' with Beckett for the better part of three + years.   I would love to see this played out.  Doing the application, studying for the exame, maybe even wonder if it would push him towards a permit to carry. You know he's always wanted that…. 

Castle loves to solve a crime but he hates the paperwork. Beckett can attest to that. The romance would be short lived for him if he had to do it without Beckett. She makes it fun and challenging for him. After Gates kicked him out of the precinct, he didn't make an effort to get back in because Beckett wasn't there. She shows back up and he couldn't make a call fast enough to his buddy, the mayor.

Now, I can see him becoming one as part of his research for one of his books but that would be the extent of it. I can see a story line where Castle meets a beautiful PI who invites him to shadow her. He accepts much to the dismay of Beckett. Jealous Beckett goes ballistic when she see them building theories with each other. The twist is that the beautiful PI is more interested in Beckett than Castle. Of course, Beckett doesn't find out until the end of the case.

cpm said:

Good points, my original thought of this was 3x01 and how it might have served him early in the ep.  More recent would be his current "secret" case of Becketts.  Might work in his favor if he was a legit PI in dealing with that? 

Again, why become a PI and do all of your own leg work when you have the NYPD and their resources at your disposal? E & R and Lanie would be more than willing to help him while keeping it on the down low from Beckett or Gates. With his money, he can hire a slew of PI to help him with the case. Besides, he knows people. He have contacts in the CIA, mob, etc. I don't think Jordan Shaw from the FBI would turn him down if he ask for help.

It's a good thought, but Castle has too much fun shadowing Beckett to make it a solid commitment that would come along with getting his license to be an investigator.  Like Nathan always says, Castle is on a daily field trip with Beckett.  He can come and go as he pleases, skipping out on paperwork if he wants, and doesn't have to always follow the rules in his current capacity.  He is in some ways more useful to the team as he is.