To make money as a business for sale broker … You will need a commercial realtors license.
It will take some training to be able to start a real estate brokerage specializing in listing and selling businesses OR commercial investment properties.

However, … once your training is done .. You can easily bank $200,000 a year OR more.
The trick will be to specialize your business sales skills …. in retail, manufacturing or marketing businesses

Another way to make money as a business for sale broker … without going through training, will be to startup a directory that lists businesses & commercial properties for sale. .. Just market the website and give customers access to a password that allows them to list their business for sale. You can charge them a monthly fee per business listing.
But the money wont be as big as a real broker.

You see… as a broker, .. If a business sells for, lets say $100,000 … You will get a nice percentage. Unlike when people just list on your website, where you charge only $60/month a listing.

So, my advice will be to go with the quick training and setup a real good profitable business.
Which ever way you decide to go …. They will both make money with the right business plan & strategy.