If you want to share your ideas and dreams of sustainable housing with others, you may want to consider to join a housing association or cooperative as this provides a lot of advantages:
If you create the buildings as a housing cooperative, you can divide the cost of the land aquisition, the financing and planing.
The greatest potential for cost saving is the infrastructure. The prices for water and electrical and even more traffic connection often exceed the price of the land. Distributing these costs by several members has the most significant impact.
Since transport and work are the most expensive factor of the reconstructable house, building houses in a group reduces the costs a lot: You need only 1 transport for material and worker. This applies even more to maintenance phase.
An often overseen advantage is the fact that you need less land. The reason is the building law prescribing minimal distance of the house to the land boundary. Inside the lot the distance of the buildings is mostly undefined. This reduces the surfaces needed by law.
Increase financial power
Buying a piece of land is becoming more and more expensive. Therfore it is a great advantage to bring the money of several individuals together. This will allow you to buy a bigger lot then if you buy it on your own. As mentioned above it also allows you to use the lot more efficiently by sharing the infrastructure.
Apart from the infrastructure house cooperatives can build and share other structure. Typical examples are shops, workshops, kitchen, shower and a common heating cabin.
In addition you can share the organisational effort needed to maintain the building and the environment.
And the advantage beyond price is the fact that you have a social group and environment to interact and exchange experience.