Hey Johnathan,
There are a couple ways you can go, becoming a Mortgage Loan Originator (MLO) also know as a loan officer, where you would either work for a bank or Mortgage Broker. Or become a Mortgage Broker. Both positions would need to be licensed but the Mortgage Broker would also have other requirements. I would recommend becoming a MLO and working for a Broker first, because there is a lot to learn.
The only time you would not need a license is if you work for a large financial bank (ex. Wells Fargo) were you would only need to be registered with the NMLS. That's not to say they would hire you without the license but they could if they wanted to.
In terms of obtaining clients it would depend on where you work. If you work for a large bank you will get people walking in the door looking for loans but you will still need to make calls to acquire more clients. If you work for a mortgage broker you will usually have to find your own clients but occasionally you can work under another MLO or mortgage broker and they will provide you leads in exchange for a cut of the commission.