DM's make tips if they are lucky and get air fills. DM's on boats are usually instructors. A regular Dm in a resort is not worth much since they cannot teach many courses if any. Instructors can make a living if they are willing to work their butts off day in and day out. Of course it depends on what you call a living. It would be rare for a new instructor right out of a school to get enough to really live on. There is just not enough time for the experience that many resorts would expect. And it depends on where you want to go. I have no illusions about making a living as an instructor at this point. It is simply extra cash to pay for my fun dives and a tax write off. Of course I'm not in a diving mecca. But if I was I;d be sure I had another source of income to rely on and use the diving as extra cash. Be prepared as a new instructor in a resort to be low man on the totem pole and get the jobs no one else wants.
I have seen very good instructors get to the boat at 6 am, fill tanks, load them, check the stores, check in divers, ride out with the first trip, give a briefing, lead a few divers, come back in, unload, fill more tanks, grab a sandwich, reload for the afternoon, take that trip out, come back, unload, wash down the boat, rinse and put away gear, and get done around 7 or 8 Pm for tips and min wage. And if the shop has a number of instructors they may only get 2 or 3 days a week. They may get some classes but they will usually go to the senior instructors. Also not really that familiar with Hall's though I did consider it 3 years ago. At that time it did not seem like too bad a deal until I also started to read about and see what are known as the zero to hero programs. Kinda woke me up real fast. If you have no kids, no wife, no real obligations go for it. the worst that can happen is you have to get a "real job" and teach on the side.