In our studio/guest quarters, we’ll have a bathroom. At first, we were just going to put a sink for the studio, then we thought we should add a toilet (because we’ll have plumbing out there anyway). Finally, our developer convinced us to go with a full bath. Having an extra bathroom and bedroom detached from the house is seen as a rental possibility, and this increases your home’s resale value. A small, pre-fabricated shower–like the ones below–will give us a full bath, and they are fairly inexpensive to buy and install.
image from Freshome
image from Components Electronics