How to run my plumbing in a building.?

I am converting a storage building into living space A kind of get away for myself. I live at home to help take care of my grandmother so I need to stay close but I want a space of my own. I live out in the country so moving into a place of my own is out of the question. we have came up with the idea of purching a storage building and running power water and cable to it from an existing garage on our property. Iam running into a problem though when it comes to a toleit though. Im very unsure of how to accomplish this. I do not have the funding to dig a septic tank. The location for my "house" is too far away form the existing tank for our house. I'm not going to be takeing showers or anything major but I need to know what to do about the drainage, from the water for washing cups and hands and the toliet. Any advice would be greatlly appreciated.