In terms of equipment: the real trick is to be friendly in the industry as much as the tourist/instructor side.
Guys who are thick into diving service all their own gear. You have a really nice setup and can make it last for twenty years, if you don't wear it to pieces beforehand.
You become an authorized dealer before companies certify you for repairs. Once certified for repairs, they send you parts kits. Access to parts and certified knowledge let you extend the life of your equipment indefinitely.
Guys who are thick into diving service all their own gear. You have a really nice setup and can make it last for twenty years, if you don't wear it to pieces beforehand.
You become an authorized dealer before companies certify you for repairs. Once certified for repairs, they send you parts kits. Access to parts and certified knowledge let you extend the life of your equipment indefinitely.