Ask HN: Suggestions for Meeting Co-Founders

I have a friend who has an idea for a startup / mobile app that he wants to start developing. He has some amateur programming experience but is looking for another developer to work with him on the project. I'm currently employed and not doing any consulting work at the moment so cannot work on his project but am trying to provide some advice.

He has some budget and was looking for a developer to hire to work on the project. I was thinking it would be better for him to find a collaborator (if not co-founder) than just a contractor for hire---even if this collaborator would need some stipend to cover their time.

It has been a few years since I have been working with any early stage startups or trying to do my own so I wanted to ask out for advice on how and where to look for a co-founder.

He is going to be moving to New York City soon so I'm curious if anyone has any in-person suggestions for him to meet folks (I'm from Boston-area myself so don't have suggestions in NYC). I'm also curious if anyone has any suggestions a "job board" of sorts but for finding co-founders (co-founder internet dating?)? Both to help him look for someone before he finishes his move to NYC and also because he may be interested in collaborating with someone remotely.

I didn't feel like I had any up to do date suggestions for my friend so any suggestions y'all may have would be appreciated.

Thanks!