Developers who aren't using any finance will need to invest most - or all - of their savings and assets into one development.
You'll need the cash for the land purchase, the build costs, and associated fees until the construction is finished and you can sell the property.
In most cases, that means being able to finance one development at a time.
Development finance means that developers can look to complete multiple developments at a time and not rely on investing all of their savings into one property - which is a much higher risk scenario.