Based on the steps listed in previous posts, purchasing the tavern is not part of the goals, but collecting from it is. I chose to purchase it early and level it up to level 2 so that it will be ready to collect from immediately when I reach that task in chapter 4.
Ps. Kattkrazie has already posted that the tavern will still work if it's above level 2. I chose to stop at level 2 until I know what resources I'll need for the rest of the chapters. Don't want to use something I'll regret not having later. Lol