My experiences as a DM differ from most in that I a. Crew a local (Socal) boat exclusively, and b. am paid for it. It is not customary here for divemasters to lead dives here; divers are on their own unless they specifically hire a DM ahead of time. I do guide trips occasionally--maybe once a month. That means I do working dives very rarely.
I don't assist with classes or work in a shop. My duties include deckhand work, filling tanks, briefing on sites, and generally helping divers get in/out of the water while having a good time.
I'm even covered under the boat's insurance policy so long as I am working under that umbrella.
But even though it's paid work, it's not a reliable, livable income. Boats get cancelled, weather happens, tips vary, and I can't even imagine having my ability to pay rent be contingent on the swell forecast.
It can be gratifying work, though. The days can be long and hard and soggy and cold, but the smiles on divers' faces when you've been in some way instrumental to their dive's success is priceless.
There are other more tangible benefits: When I'm not working, I dive off the boat for free (sometimes picking up a last-minute guiding customer), and I have access to the compressor, nitrox system, etc. I haven't had to go to a dive shop for a fill in years.
I have no desire to become an instructor. If I wanted to progress in the diving industry, I might pursue my Captain's license.