Community Land Reserves (called Community Land Trusts in the US) have been in existence around the world for over 40 years. They are non-profit organisations with a mission to provide affordable housing to low income groups, for all time.
Someone starts one off by providing a gift of land. The organisation then takes this gift of land off the market to hold it in trust forever thereafter. Ownership of the land remains with the organisation, which cannot sell it. Individual parcels are given out to owners who build on them and own the construction but not the land. On resale, the owner recoups the cost of his construction, adjusted to present-day value, but not the appreciation in land value. As a result, the incoming occupant can also get housing at an affordable price, because it is unburdened by land value. Critical to success are the format of governance of the organisation and the resale formula.