Instead of a very expensive looking X-Y-Z gantry which looks like it needs a crane to erect and a pre-made concrete foundation, instead use 3 posts in a triangle.
Each post wouldn't be need to be set into the ground - it could be just placed on dirt. Each post is held out with guy-wires to weights (rather like a circus tent is held up), and inwards with cables to the top of the other posts. The whole lot could be light enough to put up by hand. The "weights" could be water bags which can be filled with a hose when put in place.
Then, from the top of each post you have a cable inwards to your 'print head'. The print head uses three winches to pull on these cables to get to anywhere in the x-y-z space.
Obviously, such a system will have flex and wobble - which isn't great if you need perfect alignment for building your house. Thats solved by using laser angle/distance sensors to surveyed markers around the base of the house, and a continuous feedback system, allowing any flex/wobble of the structure to be compensated for.
As a bonus, with 3 additional cables from the head to the towers and 3 extra motors (which can be cheap), you can get a 5 axis machine allowing the printing of non-flat layers, allowing overhangs, arches, sculptures, etc.