An old plumber friend wished he’d specialized. His idea was 1) live in a college town with tons and tons of student or vacation rentals (we already did) and 2) just do water heaters. 24 hour service and mark up for unscheduled installations.

Easy, clean, indoor work (generally) that you can get really good and you can pretty much name your price because everybody freaks when they don’t have hot water or it is leaking.