Greg began his career as an Engineering Officer aboard ship with the US Navy in 1968, serving in the Pacific and Viet Nam.  After being discharged honorably from the Navy in 1970, Greg got married in California.  Greg and his wife then moved to his home town, San Antonio, Texas, to start their family. 

Greg was employed by MBC Consulting Engineers in 1970 where he helped design subdivision streets, lots and drainage.  From 1971-1973 Greg worked at Southwest Research Institute in a Multi-disciplinary Highway Safety study for the Federal Government.  From 1973-1979 Greg worked for Trinity Testing Laboratories in San Antonio, which later became PSI.  At PSI Greg managed the Department of Soil Investigation and Design, and the Department of Construction Materials Testing and Inspecting.  Greg was licensed to practice Engineering in the State of Texas in 1974.  In 1979 Greg opened the offices of Sethness Engineering Services in San Antonio, Texas.