A- The short answer is that the only requirement is that you must have spent an hour in an International House of Pancakes at least once in your life. The vast majority of travel agents are unlicensed and not, in any way certified. The more professional agents will take courses and seek product certification as they spend time in the industry.
The best path to a worthy entry into travel is to decide what kind of agency might come closest to meeting your interests and then find the very best one. See if the owner will hire you as an intern in your area of interest. Don’t expect to handle clients for six months. Oh, one other thing. Please don’t even consider entering this industry unless you have lived and traveled abroad for at least six months. That’s how you get a “Real Life License”.