The answer to this question depends on whether the originator is independent or employed by a lender.
Mortgage brokers are independent of any one lender and work with a variety of products across lenders. They are paid either directly by the client or – more commonly – on a commission from the lender they give a loan to.
When an MLO is an employee of an individual lender, they work exclusively with that institution's product offerings. Pay structure is going to be variable depending on company policy, but it's typically a combination of commission plus an hourly rate or salary.