You may be able to get a broker let you sit in for a day or so, and let you learn about the proffession. Or speak to one of the large franchisors about a franchise, they will give you a run through of how it works.
It is less viable than it used to be due to commission cuts, though there are many successful mortgage brokers out there.
The pay varies enormously. There are very few if any brokers working for a wage. Most would be self employed in the true sense of the word, the rest would be commission only contractors with or without a regular retainer.
Commission varies from Lender to lender, and each agregator has diferent structures as well. On average you might conservatively do your sums on .4.5% upfront and .1% trail, with the average loan 4 years, and the trail not paid until the second year.
Most would suggest having at least a years income ready, as the pipeline from client visit to payment is quite long. Also have a marketing strategy and budget ready.