Noob question but can a Polearm Master carry a 2-handed weapon as a secondary weapon?  I'm not talking about dual wielding, just carrying a 2 hand sword or axe as a secondary weapon?

many thanks!

You can carry a two-handed weapon in one hand. You just can't attack with it. The polearm master feat does not change this fact.

There’s nothing stopping you from carrying multiple weapons except encumbrance. If you mean can you hold it in one hand and use a different weapon in the other that should work too. But if you wish to use that weapon you need to sheathe or drop the other weapon. 

You can carry multiple weapons, armors, shield and other equipments. Limit beyond  emcumbrance is based on what you wear or wield.

perfect....I appreciate the input.   Looking to have a backup  2-handed weapon to my Polearm  to continue Great Weapon Master benefits.  

The fighter in one of my campaign is carrying a shield, a longsword and an halberd, so in a fight he can go sword and board for better AC, or polearm for better reach/damage. 

Smart move, and probably a pretty cool look too.