New Build HomeBuy enables people to purchase 25-75% of the property by way of a mortgage or cash purchase and you will then simply pay a subsidised rent on the remainder. This is a type of Shared Ownership.
Should financial circumstances improve then there is the option to purchase further shares at a later date. This is known as "staircasing". There is the option to purchase 100% of the property which grants the owner the freehold of the property.
Please note that in rural developments, staircasing may be restricted to a maximum of 70% or 80% ownership. If you are not sure about any restrictions that apply to the property then please ask.