With regard to DM work around Dubai it is scarce to say the least. Places like Al Boom normally don't pay DM's but rather they see the boat trip as payment enough. There are a bunch a independant instructors around who always need some help with their classes and pay generally tends to be around 300dhs per day (full day). They only tend to use DM's that they have expereance with, i know a bunch of instructors that i help out on the weekends and normally don't take any pay from them - just a couple of beers in the bar afterwards. Your best bet is to hang around one of the dive centres and strike up a couple of relationships. You need to understand that independant instructors have quite a hard time (especially now in the summer) and a day on the beach in 50 degrees isn't the most enjoyable........
On a side note, the network is great and once you get to know one or 2 then you very quickly get to know a lot more of the instructors both on the dubai coast and on the east side, BUT, DM'ing full time is not somethign you could make a living out of especially considering the current cost of living over here!!
Hope this helps?