If you build the cottage, you can always get a portable toilet that you can dump every couple of days into the house toilet. you can curtain off a corner or build a closet for it, just don't put it in until the building inspector has done his job.
Several years ago, I had a lot in Florida that we used as a base for fishing. Until we had $$$$ to build a real dwelling there, we had a large wood storage building put on lot and used porta-potti in curtained off corner. With electricity, we set it up basically as a efficiency apt except for plumbing. Eventually we had well dug and then had water outside. Sold it before we got any further.
