Which would be my best bet for a portrait lens?

[bells]

By my definition of professional, it's quite possible your 'mentor' is not a professional photographer.

Why's that?

 

[RichardsTPF]

I'll 8th the 85mm comment. 50 wouldn't be bad for showing the subjects full body in the surroundings, but for close up/bust shots with a 50mm you'd be waaaay too close for comfort!

Are you talking about FF or crop body?