The Spanish "pozo negro" (cesspit) built for us by our Spanish builders, this is it in the early stages shortly after the JCB had dug the hole, the breeze blocks are for building a wall all the way round leaving 3-4 inch gaps the first three rows from the base to allow waste to "seep" away, the pit is roughly 20ft deep to allow for a good solid covering of earth on the top when finished. You can just see the 5" waste pipe (top left) which was 72 feet long and had to be on a gradient (make sure you have your spirit level!) The system works well indeed, is hygienic and common practice in rural parts, however if you live in a built up area there should be mains sewage but there are some odd exceptions.
The picture is a bit dark but this is our living room shortly after all the trench digging and leveling the earth floors, once the pipes had been buried it was a matter of mixing up a tremendous amount of concrete and laying the floor - this took 2 days, 1 day to lay the floor tiles, 1 day to prepare the walls for paint, 1 day to paint and the finishing touches as and when, overall if you realy get stuck in reckon on a good week to complete a normal room (kitchens and bathrooms obviously take longer) Myself and my partner completed this work in the time mentioned above and that included looking after our little boy who was always trying to help! (at not even 3 at the time he could mix plaster with the best of em!!)
And the living room a few days earlier... If you want a smooth plaster finish *(see post on yeso) allow much more time, as it was we went for the rustic approach and used a sponge float for a textured finish.