Buying a new truck is more for reliability and need than a tax break. He should look at other ways to invest in the business and see if he can shift that money into a SEP.
His business is doing inspections for lenders on new construction, to verify the work has been done properly and passed by the city/county building inspector.
He has a 75% pension from the govt job he worked at for 29 years.
A vehicle is the only investment his business needs.