Yes, but that's not really during levelling. The treasure missions require level 100 and unlocking (if that's your first Inn) thru a series of heroic dungeons (I don't think there's enough non heroic dungeon quests to get the required 10). And if you're leveling regularly, then you're going to get 100 and have 20+ followers within 2 to 3 weeks in the most casual cases.
The real question is not if you're going to build an Inn. The Inn is exceedingly useful later on, to recruit additional followers if you have a bad luck and can't ensure a 100% chance on all raid missions, and then those treasure hunters and scavengers. And the treasure missions. But while leveling, you don't need the Inn, and so, you may use a trading post or lumberyard for extra ressources, which will help you to have enough GR to finish your garrison once you ding 100.
Either the dwarf/forsaken you get during the intro quests (if you want extra dps) or the tanky type in Talador will do (if you're a squishy caster). You can forget or disable the rest.
PS: I always cracks me that the tank Paladin draenei ends up with... the warlock ability from her equivalent in the horde. There's a lot in that expansion that was done for one path, then filler stuff done at random for the other. For example, pick the Gladiator Pit in Gorgrond if you want to make sense of the questlines. The other side is completely irrelevant, and when you arrive at the end of the quest, you have absolutely no idea why that commander is all upset about some artefact that you're told to use and have no idea where it came from, and that he shouldn't have left it to some orc you've never heard about, or why you have a lone giant Raven bird waiting for you to go back to your outpost.
You can use your raid leader's garrison Mage Tower, since the mage portals drop you next to Highmaul or BRF.
(if your raid leader doesn't have one, nominate the one who does)