There's not really a training or certification you can take to become a
travel agent. Generally speaking, travel agents have to be certified by CLIA or IATA to receive travel agent access and commissions for bookings. Typically, those certifications can only be first obtained by working under a larger entity agency (i.e.
AAA, Liberty Travel). Once an agent makes sales of a certain amount and has client base, you can go independent but I believe there are sales minimums needed in order to maintain IATA or CLIA certifications. Frankly, its best to work under a larger agency first anyhow, especially if they are paying a draw or a base salary. Travel agents make their money through commission only, so until you have a good client base and make a significant number of bookings, the income is not much.
If you're just interested in planning Disney trips, there's many authorized Disney travel agencies that exist that take on "travel planners" as independent contractors. They work in the same capacity as a true travel agent, but work under the umbrella of the parent agency which provides the IATA/CLIA designation. In my own experience, you work for this company and have the benefit of their name and marketing, they cover the cost of you to complete the Disney College of Knowledge, and they split commissions with you when you complete a booking. I worked for one that I won't name due to board rules, and commissions were split 50/50. They sent commission checks monthly and deducted the cost of facilitating/mailing documents to clients. Disney commission is not great so I barely made money off this. I would have had to dump a lot of sweat equity into marketing myself, building a brand, drawing in clients. Commissions are made after the client travels, so I had to wait a few months to see any return. I was doing it for fun on the side, so I wasn't able to parlay it into anything beneficial for myself. The agency also didn't provide leads, so you had to generate your own. Other agencies may vary, but I think the model is probably fairly consistent. I don't mean to sound discouraging, but its important to know its not lucrative and should be looked at as more of a fun venture to help others rather than a money-making career move.
Alternatively, you could look at a nationwide type of endeavor - working from home for Disney, AAA, Liberty Travel. I don't know what the demand for travel planners in the current environment would be, but never hurts to search for openings! I worked as a travel planner at AAA briefly as well. I was paid hourly and received a portion of my commission, though my hourly rate was my main pay. Obviously it was easier to get bookings at AAA, but I also wasn't receiving as much commission from them either.