You generate high income by working very hard, long hours. Being available at all hours of the day and night and spending time learning your profession and marketing.
that is just the short list.
Oh, yeah, and a little luck won't hurt!
In my opinion, you have to look at a business in Real Estate the way you would look at entering any business, there are many expenses the first few years and you do not see a return right away.
Your other fees that you asked about depend on what firm you associate with, as some firms nickel and dime their agents to death and some, like mine, do not charge fees to agents. We make our money on a percentage of the agents' deals.
I would talk with several companies to compare, but these are ancillary to the real question - how do you make real money doing this? The answer is to find a mentor who will bring you along.
I would recommend you interview with a few brokerages and ask very specific and detailed questions about fees and so on. I personally hate surprises, I want to know exactly what I am going to pay and when, so I can plan accordingly.