Unlike Batman and Iron Man, both billionaires capable of funding any operation they like, the Power Rangers don't appear to have substantial resources. How do they back their operations financially? Running humongous robotic machines to defeat giant monsters sounds like several millions of dollars, if not billions.
By and large, the Power Rangers teams do not need substantial financial resources.
Virtually all of the Power Rangers equipment and abilities are created or powered by the Morphing Grid, which is a universal energy field which some things are capable of tapping into.
The Zords, while seeming mechanical, do not operate as mechanical devices would. They do not seem to require regular maintenance, they are seen to be completely changed by Morphing Grid power.
Given that many of the Rangers other tools are created similarly (in flashes of energy, either during morphing or post-morphing), it stands to reason that most of their gear is supplied by (and maintained by) the morphing grid itself.
Some beings, such as Zordon and Alpha 5 from the original show, are knowledgeable in the applications of the Morphing Grid energy and can harness it to specific purpose (such as the Command Center's teleporters). It's reasonable to assume that these people are the primary source for most of the Ranger's specialty gear.
Sometimes Rangers themselves learn how to harness this ability. Billy, for instance, created tools which let the original Rangers interface with the Command Center's existing technology. Later, after giving up his Ranger abilities, he continued to aid the later teams by providing technical support.
Some Ranger teams are legacy teams - a good example is the Mystic Force. They are taking over for a previous team of Rangers and learn to use the same equipment and tools which the previous team used.
By and large, the Power Rangers do not need substantial financial resources to do their superhero work. When they do need something that the Morphing Grid does not provide, it tends to be a plot McGuffin which they can locate and secure by adventuring, not something they would have to order on Amazon.