Is long hair frowned upon?

I was in a similar situation last year. Grew out hair during senior year, ended up liking the new look, and was not sure if it would be appropriate for the office. I ended up keeping the long hair for my full-time start date. So glad I kept the long hair. As long as you're not walking into full-time training with a mohawk or ridiculous haircut, then no one gives a shit what haircut you have as long as you produce good work and are chill to work with. I'm at a BB and several people in my group have longer hair than the typical conservative finance haircut. One of the top MDs in our group has a ponytail lol.

Long hair on men is not common, but I have seen male staff with long haircuts before. I would say it depends how it looks, but ultimately this is your decision.
In fact, most men I know are balding so much they wouldn't be able to do this anyway. So maybe it is about who can do it instead of whether it is appropriate.

My general feeling is that as long as it's well kept and professional, you should be okay. Just be prepared for some funny looks and a comment or two.

The main caveat I would make is that the rest of your appearance should be super conservative. 

Be careful, few people can pull off the long hair and beard combo. My girlfriend told me I looked homeless, and looking back at photos of us she was right lol.

So now days I choose one or the other. Short hair with beard. Long hair, clean shaven.

I would consider losing the beard but you should be fine with the flow if it is well maintained

Second/third losing the beard, the combo is too Neanderthal, but long hair alone is fine. Your attire needs to be otherwise excellent, especially early on. If your hair is styled and you dress well people will think you're just fashionable.

Small update, rocked it for my first week or so. The beard was not an issue as it has p much filled in. However, I felt really weird with my hair lol as I was the only one in my office with hair this long. The back goes a bit past my shoulders. So I decided to slightly cut hte back so that it is no longer than what a normal cut would be. Other than that kept everything else constant. The end result was a hairstyle similar to a Neal Caffrey but a bit longer. I think I will try to rock this for a few months. Thank you for the input.