Preston was married to Kathleen Marchant (1936-2017) until her death. He lives in Cleveland. His residence is located in the Anatole subdivision off of U.S. 11 near the residence of fellow businessman Allan Jones. He is of the Baptist faith, and attends First Baptist Church in Cleveland.

Preston moved to Cleveland, Tennessee in the late 1950s a few years after his brother Winton Russell Preston, who had come to study at Southern Missionary College, now Southern Adventist University in nearby Collegedale.

In 1970, Preston founded Life Care Centers of America in Cleveland, and is the sole owner, chairman and CEO. It later grew to be the largest privately owned long term care facility chain and the third largest privately owned long-term care facility in the United States.

Together with his brother Winton, he co-founded a company called Hospital Publications to create patient booklets and public relations materials for hospitals, and the company operated until 1972. The idea had come from his work in hospitals, where he concluded that there was a need for better public relations in the Health care system. Through this Business, he observed the conditions of elderly patients in hospitals, and concluded that there was a need for better long term care.

Forrest Lee Preston was born and grew up in Massachusetts, the son of a Seventh-day Adventist pastor Father, Benjamin M. Preston and his wife Ethel Preston. His Father died in 1994, and Preston endowed the Benjamin M. Preston scholarship at Atlantic Union College, of which his Father was an alumnus.

As of September 2015, he had a net worth of US$2.1 billion.