You don't. No time, and mostly no gold to do it. Most have no gear and few have mounts, much less professions, besides possibly a collection one. 90 days will go by quickly and if you are doing more than 1 team I would lvl first and then worry about professions after that. Even with my meager stash of gold (between 4 and 5k) I will be hard pressed for gold by the time this 90 days is up. After training on 5-10 toons, mounts and gear there is nothing left for professions. After the leveling is over and the time limit isn't pressing up against me, I will take a breather and figure out which toons and what professions will work for me.