[flagrant_taco]

This also depends a lot on your locality. If you live in an area where septic tanks are allowed you don't have to pay for city sewer usage.

You can also skip that entirely with a composting toilet. Again depending on your local laws, gray water can often be drained directly outside, potentially through a leech field if required. Plenty of areas allow this for specific uses like washing machines, the only reason it can't be done with standard toilets is because of the solid waste.