He then completed a two-year religious mission for the Church of Jesus Christ of Latter-day Saints in France, returning to Ricks College in 1972.
He served as vice president of development for the McNiel/Mehew Group in Salt Lake City, Utah.
In 1983, he returned to settle in south-eastern Idaho and in 1985 established a mortgage company, First Financial Corporation.
Mortimer has served on the Board of the Idaho State Mortgage Bankers Association and was its president from 1991 to 1992.
Mortimer also has interests in residential and commercial development, having launched Comfort Construction in 1998 and Commerce Properties Investments LLC in 2002.