As I am still doing my PADI DM, I have just read the manual over again this weekend when I had some spare time. I do not see any rule specifically where its says " 3. As a DM you MUST own all your own gear and use it every time." Though it does mention that you are a professional and are expected to dive with the current gear used in the sport. Now I am a poli sci major way back when from undergrad (i.e. natural politician who does not want to be a politician) so i could convice you either way. But for me, interpreting what these books are telling me (think we call it here "good judgement" and "intention of the rule") i think it is safe to say that as a DM you should be expected to own a complete set of gear because you are going to be responsible for leading new and experienced divers when they ask you for help.
For me this does not mean that i must have the new (insert brand, model, piece of equipment) to be a DM, but I should have a set of something presentable, in good condition, that sets a good example. As I have said before, the rest of that is marketing and subject to the policies of the dive shop where you work/rent gear from. There is nothing in any of the rules mentioning that you must have what the LDS has.
If I am a independant professional carpenter, I may not have all the top of the line saws, drills, etc, but I should have A saw and A drill. If I am reasonably proficient and do this work often enough I will use these tools enough and buy a new piece of equipment now and then when the old piece is worn out and does not do a good job.
If I am a professional construction company, I will have my own equipment and hire people with the best skills to come and use my equipment because I want to ensure the best quality work is done, again, replacing when necessary.
If I am a handyman, I work with whatever is at hand at the moment.
For me, yes, I am buying now a full set of all my own gear. I have been going piece by piece for a few years now, but heck, I love diving and, yes, as a professional I believe that I should own the basics to perform my trade, whether I do it on the weeked or every day. Obviously what really matters is the quality of the service I provide to people who choose to dive with me, but I can get it done without a brand new set of equipment.
Back to the carpenter analogy, depending on what I need I will contact one of the three above. The question is what do YOU want to be or where YOU want to work for. Diving equipment is means to an end and sacrificing the means to reach the end is not how I roll/dive.