Cartwright spent one season in 1973 as an assistant coach at what is now called Liberty University under Lee Royer. But after Royer died in a plane crash, Cartwright was named the school's second ever head coach and he spent three seasons leading the Flames.
Cartwright founded Calvary Independent Baptist Church in the Philadelphia community of Morton, Pennsylvania in 1977 shortly after graduating from Liberty Baptist Seminary. He remains the only senior pastor of the church after over 30 years. He also began Calvary International Christian School as a ministry of the church.