tenover, the work requirements are going to vary with the type of operation through which you are doing your DM, and perhaps a bit what your goals are.
For my DM, I assisted with classes -- that meant I showed up at the academic sessions twice a week, helped issue equipment to the students and solve problems. I sat through the lecture sessions, corrected quizzes and knowledge reviews, and helped students get their gear to their cars. At the pool, I helped carry gear and supervised gear assembly, and I then dove with the class. Afterwards, I'd go back to the shop and help check in the class equipment, rinse it and hang it up. These days began about 6pm and ended at midnight, and that was Monday and Wednesday of each of three weeks.
On the weekends when we did OW dives, I went to the dive site, helped put in the float and line, and helped move gear and supplies for the class and get them set up near the beach. I helped students with their equipment. I was sometimes asked to do the site briefing. I dove with the classes, then helped students swap out tanks and supervised to make sure they stayed warm and were okay. We did the second dive, and then I helped everybody get their stuff back to their cars, and brought back in the float and the extra weights and all the supplies we'd unloaded. These days began about 7am and ended around 2 to 3 in the afternoon. This was one day of each of two successive weekends.
Other than that, I was not expected to work for the shop, but I did my DM through a local dive shop here in Seattle, not a residential program like some of the DM classes in Asia are.
To the OP -- I have a vague memory that I was unable to assist with classes as a DMC until I had completed some of the academics -- I'll have to go review the standards, but that's what I remember.
For my DM, I assisted with classes -- that meant I showed up at the academic sessions twice a week, helped issue equipment to the students and solve problems. I sat through the lecture sessions, corrected quizzes and knowledge reviews, and helped students get their gear to their cars. At the pool, I helped carry gear and supervised gear assembly, and I then dove with the class. Afterwards, I'd go back to the shop and help check in the class equipment, rinse it and hang it up. These days began about 6pm and ended at midnight, and that was Monday and Wednesday of each of three weeks.
On the weekends when we did OW dives, I went to the dive site, helped put in the float and line, and helped move gear and supplies for the class and get them set up near the beach. I helped students with their equipment. I was sometimes asked to do the site briefing. I dove with the classes, then helped students swap out tanks and supervised to make sure they stayed warm and were okay. We did the second dive, and then I helped everybody get their stuff back to their cars, and brought back in the float and the extra weights and all the supplies we'd unloaded. These days began about 7am and ended around 2 to 3 in the afternoon. This was one day of each of two successive weekends.
Other than that, I was not expected to work for the shop, but I did my DM through a local dive shop here in Seattle, not a residential program like some of the DM classes in Asia are.
To the OP -- I have a vague memory that I was unable to assist with classes as a DMC until I had completed some of the academics -- I'll have to go review the standards, but that's what I remember.
. I had a lot of loyalty to my old shop until I felt like they were taking advantage of me or my students. Once that happens, loyalty to your students/customers is much more important. Also just remember this, they won't have any issues throwing you under the bus if this starts getting bad for them. They have no loyalty to you. They just want your money and free labor from the sounds of it.
So a smaller shop that's working at full capacity during the summer might have a harder time freeing your instructor to do this, but it sounds like you are willing to be available at pretty much any time... That's kinda weird to me that your instructor can't sit down with your a couple weekday nights to get through it right away. 
