I can tell you, as a Canadian travel agent, that number is so far out to lunch. I can just wish.
I started this when I still worked for the government, knowing it wasn't going to pay piles of money. When I retired I continued with it because I enjoy it, certainly not for the money.
I work for cruiseshipcenters (I think I can say there here.) It's now owned by Expedia.ca. I work with a franchise but very seldom go into the office. I have a number of clients I have worked with over the last number of years.
I do this because I enjoy it and the bit of extra money supplements my pension.
I don't want more clients than I can handle on a personal basis. I am available to them about 18 hours a day, 7 days a week. If I had too many clients I just couldn't give them the service they have a right to.
I still take on more clients because I have the time. But for the original question, there is not a lot of money to be made.