I don't know anything about New Zealand, but in the US, this is not an easy business to get into. True, if you have a good customer base, you can make easy money by keeping the poor poorer. But at least here, there are just too many payday type loan places. The number of customers each is thus too small for much profit.
I have a friend who owns a lot of business real estate. He now refuses to lease to any payday type loan places since they keep going out of business (meaning they back out of their deal with him without paying their lease and he has to go through all the expense again to market the place). He says the most common thing is that people sign a lease to get an address for the legal paperwork. But they never know how difficult it is to get through the legal hassles here in the US. So, they can't start business, and close before bringing in even a single dollar.