Here in the US, local government and university organizations finance community garden projects such as what you are doing. We have an organization of Master Gardeners affiliated with the local County Extension service - a combined County and university project.
The Master Gardeners are volunteers (donate their time and expertise for free) and raise money by holding a plant sale each year. Then Master Gardeners can apply for grants for approved community projects. There is oversight, and accountability in that we just show that we did indeed spend the money for the project by presenting receipts for supplies, seeds, tools, gloves etc.