The issue has been brought up since this post was asked, and since it's direct I'll answer it directly.
Yes I am living and diving and working in a third world country.
Yes I earn a barely enough to live month to month.
No there is no chance in hell I would be able to afford an entire new setup before I move on from this country.
Yes I have been provided equipment during all of my training and work, along with all the other employees local or foreign.
More importantly, I dive every day. I have more than 400 dives most of which involved assisting and teaching (I'd say 70-80% of them) students.
I bought my first set of equipment piece by piece in the Philippines. I was not being paid much... about $500/month retainer and comission if I recall. I had to pay my own living expenses so I lived in an unfurnished single room with a toilet with no seat, cold water shower and a ceiling fan. I slept on a cheap foam mattress on the floor covered by 2 mosquito nets. My neighbours were cows, cockroaches and a few thousand 'fighting cocks'. Took me a few months to get gear but I managed.
Talk to the shops and make sure you're getting a 'pro' discount. It helps enormously to actually bring a couple of guests to the shop before you talk about getting cheaper prices on gear.
Owning your own kit just makes sense as a diver. Rental gear gets abused. Regs degrade and ease of breathing is affected. Unless I'm taking care of the regs myself, I don't trust them much. Something as simple as a torn lug in a mouthpiece can really affect your concentration levels and you need to be on the ball- especially as you say that you're primarily with students.